C program to find Sum of Series : 1+2+3+4+….+N using Recursion

Algorithm : : 

• First printf statement will ask the user to enter any integer value and the scanf statement will assign the user entered value to Number variable.

• Next, we used For Loop to iterate between 1 and user entered value.

• Within the For loop, we calculated the sum.

• In the above example, user entered value is 5 it means, 1 + 2 + 3 + 4 + 5 = 15

This program allows the user to enter any integer Value. Using the Recursive and Iterative Functions we will calculate the sum of N natural Numbers.

Below is the source code for C program to find sum of Series : 1+2+3+4+….+N which is successfully compiled and run on Windows System to produce desired output as shown below :

SOURCE CODE : :

/* C program to find sum of Series : 1+2+3+4+....+N */


#include<stdio.h>
int series(int n);
int rseries(int n);

int main( )
{
        int n;
        printf("Enter number of terms : ");
        scanf("%d", &n);

    printf("\b\b Using Recursion :: \n");
        printf("\b\b = %d\n", series(n));       /*  \b to erase last +sign */
        printf("\n\b\b Using Recursion :: \n");
        printf("\b\b = %d\n\n\n", rseries(n));

        return 0;
}/*End of main()*/

/*Iterative function*/
int series(int n)
{
        int i, sum=0;
        for(i=1; i<=n; i++)
        {
                printf("%d + ", i);
                sum+=i;
        }
        return sum;
}/*End of series()*/

/*Recursive function*/
int rseries(int n)
{
        int sum;
        if(n == 0)
                return 0;
        sum = (n + rseries(n-1));
        printf("%d + ",n);
        return sum;
}/*End of rseries()*/

Output : :

/*  C program to find sum of Series : 1+2+3+4+....+N  */

Enter number of terms : 15

 Using Recursion ::
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 + 15  = 120

 Using Recursion ::
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 + 15  = 120