By | 05.11.2016

# Find sum of Series : 1+2+3+4+….+N

Write a C program to find sum of Series : 1+2+3+4+….+N. Here’s a Simple program to find sum of Series : 1+2+3+4+….+N by creating Recursive and Iterative Functions in C Programming Language.

## 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```

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