# C Program to Find the Sum of Natural Numbers using Recursion

#### In this example, you will learn to find the sum of natural numbers using a recursive function.

The positive numbers 1, 2, 3… are known as natural numbers. The program below takes a positive integer from the user and calculates the sum up to the given number.

## Sum of Natural Numbers Using Recursion

``````
#include <stdio.h>
int main(){
int num;
printf("Enter a positive integer: ");
scanf("%d", &num);
return 0;
}

if (n != 0)
return n + addNumbers(n - 1);
else
return n;
}
``````

Output

```Enter a positive integer: 20
Sum = 210
```

Suppose the user entered 20.

Initially, `addNumbers()` is called from `main()` with 20 passed as an argument.

The number 20 is added to the result of `addNumbers(19)`.

In the next function call from `addNumbers()` to `addNumbers()`, 19 is passed which is added to the result of `addNumbers(18)`. This process continues until n is equal to 0.

When n is equal to 0, there is no recursive call. This returns the sum of integers ultimately to the `main()` function.

```