i.e., any term (n^{th} term) of an arithmetic sequence is obtained by adding the common difference (d) to its previous term ((n – 1)^{th} term). i.e., the recursive formula of the given arithmetic sequence is, **an=an−1+d a n = a n − 1 + d.**

Contents

- 1 What is arithmetic recursive formula?
- 2 How do you write a recursive formula for an arithmetic sequence?
- 3 How do you write an arithmetic sequence?
- 4 What is a recursive equation example?
- 5 How do you find the recursive formula for a quadratic equation?
- 6 What is the formula of the sum of arithmetic sequence?
- 7 Introduction to Arithmetic Progressions
- 8 Formulas for Arithmetic Sequences
- 9 Using Explicit Formulas for Arithmetic Sequences
- 9.1 A General Note: Explicit Formula for an Arithmetic Sequence
- 9.2 How To: Given the first several terms for an arithmetic sequence, write an explicit formula.
- 9.3 Example: Writing then th Term Explicit Formula for an Arithmetic Sequence
- 9.4 Try It
- 9.5 A General Note: Recursive Formula for an Arithmetic Sequence
- 9.6 How To: Given an arithmetic sequence, write its recursive formula.
- 9.7 Example: Writing a Recursive Formula for an Arithmetic Sequence
- 9.8 How To: Do we have to subtract the first term from the second term to find the common difference?
- 9.9 Try It

- 10 Find the Number of Terms in an Arithmetic Sequence
- 11 Solving Application Problems with Arithmetic Sequences
- 12 Contribute!
- 13 Sequences as Functions – Recursive Form- MathBitsNotebook(A1
- 14 Recursive Formula (Explained w/ 25 Step-by-Step Examples!)
- 15 What Is A Sequence
- 16 Recursive Formula Definition
- 17 Example
- 18 Recursive Formulas For Sequences
- 19 Example
- 20 Example
- 21 Example
- 22 Summary
- 23 Video Tutorial w/ Full LessonDetailed Examples
- 24 Recursive Formulas for Arithmetic Sequences

## What is arithmetic recursive formula?

A recursive formula allows us to find any term of an arithmetic sequence using a function of the preceding term. Each term is the sum of the previous term and the common difference. For example, if the common difference is 5, then each term is the previous term plus 5.

## How do you write a recursive formula for an arithmetic sequence?

A recursive sequence is a sequence in which terms are defined using one or more previous terms which are given. If you know the nth term of an arithmetic sequence and you know the common difference, d, you can find the (n+1)th term using the recursive formula an+1=an+d.

## How do you write an arithmetic sequence?

An arithmetic sequence is a sequence where the difference between each successive pair of terms is the same. The explicit rule to write the formula for any arithmetic sequence is this: an = a1 + d (n – 1)

## What is a recursive equation example?

an=2an−1+3 is a recursive formula because each term, an, refers back to the previous term, an−1. This equation is telling us that whatever term we want to find is equal to 2 times the previous term, plus 3. The first three terms of this sequence are: 4,11,25.

## How do you find the recursive formula for a quadratic equation?

A recursive equation for the original quadratic sequence is then easy. More precisely, if the quadratic sequence is given by q(n), where q is a quadratic polynomial, then d(n)=q(n+1)−q(n) is the arithmetic progression given by d(n)=an+b, where a is the second difference and b=d(0).

## What is the formula of the sum of arithmetic sequence?

The sum of the arithmetic sequence can be derived using the general arithmetic sequence, an n = a1 1 + (n – 1)d.

## Introduction to Arithmetic Progressions

Generally speaking, a progression is a sequence or series of numbers in which the numbers are organized in a certain order so that the relationship between the succeeding terms of a series or sequence remains constant. It is feasible to find the n thterm of a series by following a set of steps. There are three different types of progressions in mathematics:

- Arithmetic Progression (AP), Geometric Progression (GP), and Harmonic Progression (HP) are all types of progression.

AP, also known as Arithmetic Sequence, is a sequence or series of integers in which the common difference between two subsequent numbers in the series is always the same. As an illustration: Series 1: 1, 3, 5, 7, 9, and 11. Every pair of successive integers in this sequence has a common difference of 2, which is always true. Series 2: numbers 28, 25, 22, 19, 16, 13,. There is no common difference between any two successive numbers in this series; instead, there is a strict -3 between any two consecutive numbers.

### Terminology and Representation

- Common difference, d = a 2– a 1= a 3– a 2=. = a n– a n – 1
- A n= n thterm of Arithmetic Progression
- S n= Sum of first n elements in the series
- A n= n

### General Form of an AP

Given that ais treated as a first term anddis treated as a common difference, the N thterm of the AP may be calculated using the following formula: As a result, using the above-mentioned procedure to compute the n terms of an AP, the general form of the AP is as follows: Example: The 35th term in the sequence 5, 11, 17, 23,. is to be found. Solution: When looking at the given series,a = 5, d = a 2– a 1= 11 – 5 = 6, and n = 35 are the values. As a result, we must use the following equations to figure out the 35th term: n= a + (n – 1)da n= 5 + (35 – 1) x 6a n= 5 + 34 x 6a n= 209 As a result, the number 209 represents the 35th term.

### Sum of n Terms of Arithmetic Progression

Given that ais treated as a first term anddis treated as a common difference, the N th term of the AP may be calculated using the following formula: In order to compute the n terms of an AP using the previously mentioned formula, the following is the general form of an AP: Example: The 35th word in the series 5, 11, 17, 23,. is to be discovered. Solution: In the above series, a = 5, d = a 2– a 1= 11– 5 = 6, and n = 35 are the values. As a result, we must use the following equations to figure out the 35th term: n= a + (n – 1)da n= 5 + (35 – 1) x 6a n= 5 + 34 x 6 As a result, the 35th term is 209

### Derivation of the Formula

Allowing ‘l’ to signify the n thterm of the series and S n to represent the sun of the first n terms of the series a, (a+d), (a+2d),., a+(n-1)d S n = a 1 plus a 2 plus a 3 plus .a n-1 plus a n S n= a + (a + d) + (a + 2d) +. + (l – 2d) + (l – d) + l. + (l – 2d) + (l – d) + l. + (l – 2d) + (l – d) + l. (1) When we write the series in reverse order, we obtain S n= l + (l – d) + (l – 2d) +. + (a + 2d) + (a + d) + a + d + a + d + a + d + a + d + a + d + a + d + a + d + a + d + a + d + a + d + a … (2) Adding equations (1) and (2) results in equation (2).

+ (a + l) + (a + l) + (a + l) +.

(3) As a result, the formula for calculating the sum of a series is S n= (n/2)(a + l), where an is the first term of the series, l is the last term of the series, and n is the number of terms in the series.

d S n= (n/2)(a + a + (n – 1)d)(a + a + (n – 1)d) S n= (n/2)(2a + (n – 1) x d)(n/2)(2a + (n – 1) x d) Observation: The successive terms in an Arithmetic Progression can alternatively be written as a-3d, a-2d, a-d, a, a+d, a+2d, a+3d, and so on.

### Sample Problems on Arithmetic Progressions

Problem 1: Calculate the sum of the first 35 terms in the sequence 5,11,17,23, and so on. a = 5 in the given series, d = a 2–a in the provided series, and so on. The number 1 equals 11 – 5 = 6, and the number n equals 35. S n= (n/2)(2a + (n – 1) x d)(n/2)(2a + (n – 1) x d) S n= (35/2)(2 x 5 + (35 – 1) x 6)(35/2)(2 x 5 + (35 – 1) x 6) S n= (35/2)(10 + 34 x 6) n= (35/2)(10 + 34 x 6) n= (35/2)(10 + 34 x 6) S n= (35/2)(10 + 204) S n= (35/2)(10 + 204) S n= (35/2)(10 + 204) S n= (35/2)(10 + 204) S n= (35/2)(10 + 204) A = 35214/2A = 3745S n= 35214/2A = 3745 Find the sum of a series where the first term of the series is 5 and the last term of the series is 209, and the number of terms in the series is 35, as shown in Problem 2.

Problem 2.

S n= (35/2)(5 + 209) S n= (35/2)(5 + 209) S n= (35/2)(5 + 209) A = 35214/2A = 3745S n= 35214/2A = 3745 Problem 3: A amount of 21 rupees is divided among three brothers, with each of the three pieces of money being in the AP and the sum of their squares being the sum of their squares being 155.

Solution: Assume that the three components of money are (a-d), a, and (a+d), and that the total amount allocated is in AP.

155 divided by two equals 155 Taking the value of ‘a’ into consideration, we obtain 3(7) 2+ 2d.

2= 4d = 2 = 2 The three portions of the money that was dispersed are as follows:a + d = 7 + 2 = 9a = 7a – d = 7 – 2 = 5a = 7a – d = 7 – 2 = 5a = 7a – d = 7 – 2 = 5a = 7a – d = 7 – 2 = 5a = 7a – d = 7 – 2 = 5a = 7a – d = 7 – 2 = 5 As a result, the most significant portion is Rupees 9 million.

## Formulas for Arithmetic Sequences

- Create a formal formula for an arithmetic series using explicit notation
- Create a recursive formula for the arithmetic series using the following steps:

## Using Explicit Formulas for Arithmetic Sequences

It is possible to think of anarithmetic sequence as a function on the domain of natural numbers; it is a linear function since the rate of change remains constant throughout the series. The constant rate of change, often known as the slope of the function, is the most frequently seen difference. In this case, we only need to know the slope and vertical intercept. = +dleft(n- 1right)To find the vertical intercept of the function, we can subtract the common difference from its first term. = +dleft(n- 1right)To find the slope of the function, we can subtract the common difference from its first term.

Because the common difference is 50, the series represents a linear function with a slope of 50 percent.

Another method of obtaining the they-intercept is to plot the function on a graph and then determine where a line connecting all of the points would intersect the vertical axis.Recall that the slope-intercept form of a line isy=mx+b.

If we know the slope and vertical intercept of a function, we can insert them into the slope-intercept form of a line to obtain the slope-intercept form of the function.

For this sequence, there is another explicit formula, which is_ =200 – 50left(n – 1right), which may be simplified to_ =-50n+250.

### A General Note: Explicit Formula for an Arithmetic Sequence

For the textterm of an arithmetic sequence, the formula = +dleft can be used to express it explicitly.

### How To: Given the first several terms for an arithmetic sequence, write an explicit formula.

- Find the common difference between the two sentences, – To solve for = +dleft(n – 1right), substitute the common difference and the first term into the equation

### Example: Writing then th Term Explicit Formula for an Arithmetic Sequence

Create an explicit formula for the arithmetic sequence.left 12text 22text 32text 42text ldots right 12text 22text 32text 42text ldots

### Try It

For the arithmetic series that follows, provide an explicit formula for it. left With the use of a recursive formula, several arithmetic sequences may be defined in terms of the preceding term. The formula contains an algebraic procedure that may be used to determine the terms of the series. We can discover the next term in an arithmetic sequence by utilizing a function of the term that came before it using a recursive formula. In each term, the previous term is multiplied by the common difference, and so on.

The initial term in every recursive formula must be specified, just as it is with any other formula.

### A General Note: Recursive Formula for an Arithmetic Sequence

In the case of an arithmetic sequence with common differenced, the recursive formula is as follows: the beginning of the sentence = +dnge 2 the finish of the sentence

### How To: Given an arithmetic sequence, write its recursive formula.

- To discover the common difference between two terms, subtract any phrase from the succeeding term. In the recursive formula for arithmetic sequences, start with the initial term and substitute the common difference

### Example: Writing a Recursive Formula for an Arithmetic Sequence

Write a recursive formula for the arithmetic series in the following format: left

### How To: Do we have to subtract the first term from the second term to find the common difference?

No. We can take any phrase in the sequence and remove it from the term after it. Generally speaking, though, it is more customary to subtract the first from the second term since it is frequently the quickest and most straightforward technique of determining the common difference.

### Try It

Create a recursive formula for the arithmetic sequence using the information provided. left

## Find the Number of Terms in an Arithmetic Sequence

When determining the number of terms in a finite arithmetic sequence, explicit formulas can be employed to make the determination. Finding the common difference and determining the number of times the common difference must be added to the first term in order to produce the last term of the sequence are both necessary steps.

### How To: Given the first three terms and the last term of a finite arithmetic sequence, find the total number of terms.

- Find the common differences between the two
- To solve for = +dleft(n – 1right), substitute the common difference and the first term into the equation Fill in the blanks with the final word from and solve forn

### Example: Finding the Number of Terms in a Finite Arithmetic Sequence

The number of terms in the infinite arithmetic sequence is to be determined. left

### Try It

The number of terms in the finite arithmetic sequence has to be determined. 11 text 16 text. text 56 right 11 text 16 text 16 text 56 text 56 text 56 Following that, we’ll go over some of the concepts that have been introduced so far concerning arithmetic sequences in the video lesson that comes after that.

## Solving Application Problems with Arithmetic Sequences

In many application difficulties, it is frequently preferable to begin with the term instead of_ as an introductory phrase. When solving these problems, we make a little modification to the explicit formula to account for the change in beginning terms. The following is the formula that we use: = +dn = = +dn

### Example: Solving Application Problems with Arithmetic Sequences

Every week, a kid under the age of five receives a $1 stipend from his or her parents. His parents had promised him a $2 per week rise on a yearly basis.

- Every week, a $1 allowance is given to a five-year-old youngster. A $2 per week boost in wages is promised to him by his parents each year.

### Try It

A lady chooses to go for a 10-minute run every day this week, with the goal of increasing the length of her daily exercise by 4 minutes each week after that.

Create a formula to predict the timing of her run after n weeks has passed. In eight weeks, how long will her daily run last on average?

## Contribute!

Do you have any suggestions about how to make this article better? We would much appreciate your feedback. Make this page more user-friendly. Read on to find out more

## Sequences as Functions – Recursive Form- MathBitsNotebook(A1

We saw inSequences – Basic Information, that sequences can be expressed in various forms.This page will look at one of those forms, the recursive form.Certain sequences (not all) can be defined (expressed) in a”recursive” form. In arecursive formula,each term is defined as a function of its preceding term(s).Arecursive formuladesignates the starting term,a1, and thenthterm of the sequence,an, as an expression containing the previous term (the term before it),an-1. |

The process ofrecursioncan be thought of as climbing a ladder.To get to the third rung, you must step on the second rung.Each rung on the ladder depends upon stepping on the rung below it.You start on the first rung of the ladder.a1 From the first rung, you move to the second rung.a2a2=a1+ “step up”From the second rung, you move to the third rung.a3 a3=a2+ “step up” | |

If you are on thenthrung, you must have stepped on then -1 strung.an=an -1+ “step up” |

Notation:Recursive forms work with the term(s) immediately in front of the term being examined.The table at the right shows that there are many options as to how this relationship may be expressed innotations.A recursive formula is written withtwo parts: a statement of thefirst termalong with a statement of theformula relating successive terms.The statements below are all naming the same sequence: |

Given Term | Term in frontof Given Term |

a4 | a3 |

an | an- 1 |

an+ 1 | an |

an+ 4 | an+ 3 |

f(6) | f(5) |

f(n) | f(n- 1) |

f(n +1) | f(n) |

The following is the sequence: Find a recursive formula that works. The following is an example of anarithmetic sequence (the same number, 5, is added to each term to get tothe next term).

Term Number | Term | Subscript Notation | Function Notation |

1 | 10 | a1 | f(1) |

2 | 15 | a2 | f(2) |

3 | 20 | a3 | f(3) |

4 | 25 | a4 | f(4) |

5 | 30 | a5 | f(5) |

6 | 35 | a6 | f(6) |

n | a n | f(n) |

Arithmetic sequences arelinearin nature. Remember that the domain consists ofthe natural numbers, and the range consists of the terms of the sequence.It may be the case with arithmetic sequences that the graph will increase or decrease. |

In mostarithmetic sequences, a recursive formula is easier to create than an explicit formula. The common difference is usually easily seen, which is then used to quickly create the recursive formula. |

This is a brief summary of the steps involved in creating a recursive formula for arithmetic sequence: 1st, determine whether the sequence is arithmetic (does each phrase add or remove the same amount from the previous term) 2.Identify the common point of disagreement. (It is the number you add or subtract from the total.) Using the first term as the starting point and the formula as the previous term plus the common difference, construct a recursive formula.

a1= first term;a n=an -1+d | a1= the first term in the sequence a n= then thterm in the sequencea n-1= the term before then thterm n= the term numberd= the common difference. | |

first term = 10, common difference = 5recursive formula:a1 = 10;a n=a n-1+ 5 |

As an example, consider the following steps in the process of developing recursive formula for an integer sequence: 1.Check to see whether the sequence is arithmetic (does each phrase add or remove the same amount from the previous term) 2.Discover the common point of difference between the two. In this case, it is the number you add or subtract from the total. Develop a recursive formula by declaring the first term, and then stating the formula to equal the preceding term plus the common difference, and so on.

Term Number | Term | Subscript Notation | Function Notation |

1 | 3 | a1 | f(1) |

2 | 6 | a2 | f(2) |

3 | 12 | a3 | f(3) |

4 | 24 | a4 | f(4) |

5 | 48 | a5 | f(5) |

6 | 96 | a6 | f(6) |

n | a n | f(n) |

Notice that this sequence has anexponential appearance. It may be the case with geometric sequences that the graph will increase or decrease. |

To explain the method of constructing a recursive formula for a geometric series, consider the following examples of writing: 1.Check to see if the sequence is geometric (i.e., do you multiply or divide by the same number from one term to the next?) 2. Calculate the common ratio. (The result of multiplying or dividing a number.) Using the first term as the starting point, and then declaring the formula as the common ratio multiplied by its predecessor, create a recursive formula.

a1= first term;a n=ran -1 | a1= the first term in the sequence a n= then thterm in the sequencea n-1= the term before then thtermn= the term numberr= the common ratio | |

first term = 3, common ratio = 2explicit formula:a n= 32n -1 |

Sequence:This example is neither an arithmetic sequence nor a geometric sequence in the traditional sense.

While we have seen recursive formulas forarithmetic sequences and geometric sequences, there are also recursive formsfor sequences that do not fall into either of these categories.The sequence shown in this example isa famous sequence called theFibonacci sequence. | |

Is there apattern for the Fibonacci sequence?Yes. After the first two terms, each term is thesum of the previous two terms.Is there a recursive formula forthe Fibonacci sequence?Yes.f(1) = 0;f(2) = 1;f(n)=f(n- 1) +f(n- 2) or a1= 0;a2= 1;an=an- 1+an- 2 | |

Notice that it was necessary to declare the first and second term, before stating the formula for generating the remaining terms. |

## Recursive Formula (Explained w/ 25 Step-by-Step Examples!)

Was it ever brought to your attention that a series may be defined both recursively and explicitly? Jenn, the founder of Calcworkshop ®, has over 15 years of experience (LicensedCertified Teacher)

## What Is A Sequence

Although a sequence is strictly defined as an enumerated collection of objects, the term “sequence” may also refer to a countable structure that represents an ordered list of items or numbers. Definition And we provide a sequence either recursively or directly, depending on the situation.

## Recursive Formula Definition

So what exactly is recursion? Often referred to as aninductive definition, arecursive definition is composed of two parts: It is possible to create the next term in a series from the preceding term or terms by using a rule, which is represented by the equation recurrence relation. To put it another way, a recurrence relation is an equation that is defined in terms of another equation.

Furthermore, all recurrence relations must be preceded by an initial condition, which is a list of one or more terms of the sequence that occur before the first term at which the recurrence relation is initiated, as defined above.

## Example

For example, List Terms Recursive — An Illustration Take note that this approach is very identical to the one we use for mathematical induction! According to Math Bits, the concept of inductive proofs is analogous to that of a staircase in that the only way to reach the summit is to walk all of the steps leading up to it. In the case of recursion, the same thing happens — each step is formed from the step or steps that came before it. An Illustration of a Staircase

## Recursive Formulas For Sequences

To summarize, a recursive sequence is one in which terms are defined in terms of one or more prior terms, as well as a beginning condition, like we just discussed. The Fibonacci sequence, on the other hand, is the most well-known recursive formula. The Fibonacci sequence is composed of the following numbers: 0, 1, 2, 3, 5, 8, 13, 21,. are the digits of the number zero. Keep in mind that each number in the series is the sum of the two numbers that came before it in the sequence. For example, the number 13 is the sum of the numbers 5 and 8, which are the two phrases that came before it.

When each number in the sequence is drawn as a rectangular width, the result is a spiral formed by the sequence.

However, employing a recursive formula might be time-consuming at times, since we must constantly rely on the words that came before us in order to construct the next ones.

All this implies is that the value of each phrase in the sequence may be determined directly without having to know the value of the preceding term.

## Example

What we will note in this issue is that patterns begin to emerge when we write down the terms of our sequences in the form of terms. The qualities of recursively formed and explicitly specified sequences may be discovered in these patterns, as can be shown in the diagram below. The sequences and summations from Precalculus, such as the Arithmetic and Geometric sequences and series, are vital to recall since they will aid us in the discovery of these patterns. Formula for the Arithmetic Sequence Formula for Geometric Sequence The Formulae for Summation Sequences Armed with these summation formulas and methodologies, we will be able to build recursive formulas and closed formulas for additional sequences that follow similar patterns and structures.

## Example

What we will note in this issue is that patterns begin to emerge when we write out the terms of our sequences in the form of terms of our sequences. The qualities of recursively created and explicitly specified sequences may be discovered in these patterns, as can be shown in the diagram above. This is a good time to review certain essential sequences and summations from Precalculus, such as Arithmetic and Geometric sequences and series, which will aid us in the discovery of these patterns. Formel de la succession arithmétique Geometric Sequence Formula is a mathematical formula that describes the relationship between geometric sequences.

The Formulae for Summation Sequences Armed with these summation formulas and methodologies, we will be able to build recursive formulas and closed formulas for additional sequences that have similar patterns and structure.

## Example

What we will note in this issue is that patterns begin to emerge when we write down the terms of our sequences. The qualities of recursively defined and explicitly specified sequences may be discovered in these patterns. Precalculus sequences and summations, such as Arithmetic and Geometric sequences and series, are vital to recall since they will aid us in the discovery of these patterns. Formula for Arithmetic Sequence Geometric Sequence Formula is a mathematical formula that describes a sequence of geometric shapes.

## Summary

Through this video, we will show how a recursive formula calculates each term based on the value of the previous term, resulting in the sequence taking a little longer to construct than a nonrecursive formula. An explicit formula, on the other hand, explicitly calculates each term in the sequence and gets a specific term in a short amount time. When it comes to the study of counting and recurrence relations, both formulae as well as summation techniques are quite useful. With these new approaches, we will be able to not only build recursive formulae for specific sequences, but we will also be on our way to solving recurrence relations!

## Video Tutorial w/ Full LessonDetailed Examples

1 hour and 49 minutes

- Introductory Video: Recursive Formula — Sequences — Summations
- 00:00:51 000:00:51 000:00:51 000:00:51 Can you predict the pattern and decide the next phrase in the sequence? Can you guess the pattern and find the next term in the sequence? (Examples1-7)
- Members Only Access to Exclusive Content

- 00:11:37 What is the difference between a Recursive Definition and an Explicit Formula
- The sequence’s first five phrases (Examples 8–10) must be identified at the time of 00:21:43. 00:30:38Recursive formula and closed formula for Arithmetic and Geometric Sequences
- 00:40:27Recursive formula and closed formula for Arithmetic and Geometric Sequences Sequences of the shapes triangular, square, and cube, as well as exponential, factororial, and Fibonacci sequences 00:47:42 Determine the definition of each sequence using a recursive approach (Examples 11-14)
- Example 15-20 show how to use known sequences to find a closed formula
- 01:22:29 show how to use known sequences to find a closed formula When working with arithmetic sequences, use the reverse—add approach (Examples 21-22). 01:35:48 Summing Geometric Sequences Using the Multiply-Shift-Subtract Method (Examples 23-34)
- 01:44:00 01:44:00 01:44:00 01:44:00 01:44:00 Practice problems with step-by-step solutions
- Chapter tests with video solutions
- Summation and Product Notation (Examples 25a-d)

With your membership, you’ll get access to all of the courses as well as over 450 HD videos. Plans are available on a monthly and yearly basis. Now is the time to get my subscription.

## Recursive Formulas for Arithmetic Sequences

A sequence of numbers is a list of numbers in which the same operation(s) are performed on each number in order to obtain the next number in the list. Arithmetic sequences are a type of sequence that is created by adding or removing a number – known as the common difference – in order to obtain the following term. In order to speak about a series in an efficient manner, we utilize a formula that, when a list of indices is entered, automatically generates the sequence. Typically, these formulae are given one-letter names, followed by a parameter enclosed in parentheses, and the expression that creates the sequence on the right hand side of the equations.

The formula for an arithmetic sequence shown above is an example of a formula.

### Examples

The following is the sequence: 1, 2, 3, 4,. | The equation a(n) = n + 13 The following is the sequence: 8, 13, 18,. | The following is the formula: b(n) = 5n – 2

### A Recursive Formula

Note that mathematicians count from one to one hundred, therefore n=1 is the first term by convention. As a result, we must first clarify what the first phrase means. Then we have to figure out what the common denominator is and incorporate it. Taking another look at the cases, we see that The following is the sequence: 1, 2, 3, 4,.

| Formula: a(n) = n + 1 | Recursive formula: a(n) = a(n-1) + 1, a(1) = 1 | Formula: a(n) = a(n-1) + 1 | The following is the sequence: 3, 8, 13, 18,. • |Formula: b(n) = 5n – 2 | Recursive formula: b(n) = b(n-1) + 5, b(1) = 3 • |

### Finding the Formula (given a sequence with the first term)

1. Determine whether there is a common difference. Remove the phrase that comes before it from the sequence by selecting a term in the sequence. 2. Create the formula from scratch. The formula is written in the following format: ‘a(n) = a(n-1) +, a(1) =’

### Finding the Formula (given a sequence without the first term)

1. Determine whether there is a common difference. Remove the phrase that comes before it from the sequence by selecting a term in the sequence. 2. Locate the very first phrase. i. Choose a phrase from the sequence and designate it as ‘k’. Designate its index as ‘h’. ii. the first term is equal to k – (h-1)* (common difference) 3. Create the formula from scratch. The formula is written in the following format: ‘a(n) = a(n-1) +, a(1) =’

#### More Information:

For additional information on this subject, please see Learn how to code for nothing. More than 40,000 people have benefited from freeCodeCamp’s open source curriculum, which has helped them land careers as developers. Get started today.