sum of first n natural numbers in c using recursion code example

Example 1: Sum of digits of a number using recursion function c

/*  
 * C Program to find Sum of Digits of a Number using Recursion
 */
#include <stdio.h>
 
int sum (int a);
 
int main()
{
    int num, result;
 
    printf("Enter the number: ");
    scanf("%d", &num);
    result = sum(num);
    printf("Sum of digits in %d is %d\n", num, result);
    return 0;
}
 
int sum (int num)
{
    if (num != 0)
    {
        return (num % 10 + sum (num / 10));
    }
    else
    {
       return 0;
    }
}

Example 2: c program to find the sum of given number using recursion

# include <stdio.h>
int sum(int number);
int main
{
 int n;
 int a;
 printf("enter a number");
 scanf("%d,&n);
 a=sum(n);
 printf("sum=%d",a);
 }
int sum(int number)
{
  if (number==0)
    return 0;
  return(number%10+sum(number/10);
 }

Example 3: recursive function to find the sum of the nth term

void recurse() {
    .....
    recurse()  //recursive call
    .....
}
int main() {
    .....
    recurse(); //function call
    .....
}