# Fibonacci series program in C using recursion

In this program, you'll learn to display the **Fibonacci** sequence using a recursive function in **C** programming language.

The Fibonacci series are the sequence of numbers in which the next number is the sum of the previous two numbers. The Fibonacci series was well-known hundreds of years earlier. The "**Fibonacci**" name came from the nickname "**Bonacci**".

We can easily remember the Fibonacci Sequence using November 23rd as the Fibonacci Day. As November 23rd has the digits "1, 1, 2, 3", which is part of the sequence.

In the above image, the first two numbers are 0 and 1. So, according to the Fibonacci rule, the third number is 1 (sum of 0 and 1). The fourth number is 2, and so on.

```
0 + 1 = 1 // 0, 1, 1
1 + 1 = 2 // 0, 1, 1, 2
1 + 2 = 3 // 0, 1, 1, 2, 3
2 + 3 = 5 // 0, 1, 1, 2, 3, 5
```

`0 ,1 , 1, 2, 3, 5, 8, 13, 21, 34....`

## Fibonacci Series Program in C using Recursive Function

A **recursion** function is a function that is called by itself. In the given example, we call the recursion function to get the Fibonacci series. A recursion function continues until some condition is met to prevent it. That's why we use the if statement to break the infinite recursion.

In the given program, we use recursion to generate the fibonacci series. The function **fibonacciSeries()** is called recursively until we get the result. In the function, we first check if the number **n** is greater than 0. If yes, we recursively call **fibonacciSeries()** with the values **n-1** and **n-2**.

```
// C program to print Fibonacci series
#include<stdio.h>
// Recursive function
void fibonacciSeries(int n){
static int n1=0,n2=1,n3;
if(n>0){
n3 = n1 + n2;
n1 = n2;
n2 = n3;
printf("%d ",n3);
fibonacciSeries(n-1);
}
}
int main(){
int n;
printf("How many number of series? : ");
scanf("%d",&n);
printf("Fibonacci Series: ");
printf("%d %d ",0,1);
//Call Function
fibonacciSeries(n-2);
return 0;
}
```

**Output 1**

```
How many number of series? : 15
Fibonacci Series: 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377
```

**Output 2**

```
How many number of series? : 20
Fibonacci Series: 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181
```

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