Write a c program to find out the sum of in A.P. series

#include<stdio.h>

#include<math.h>

int main(){

    int a,d,n,i,tn;

    int sum=0;

    printf("Enter the first number of the A.P. series: ");

    scanf("%d",&a);

    printf("Enter the total numbers in the A.P. series: ");

    scanf("%d",&n);

    printf("Enter the common difference of A.P. series: ");

    scanf("%d",&d);

    sum = ( n * ( 2 * a + ( n -1 ) * d ) )/ 2;

    tn = a + (n-1) * d;

    printf("Sum of the series A.P.: ");

    for(i=a;i<=tn; i= i + d ){

         if (i != tn)

             printf("%d + ",i);

         else

             printf("%d = %d ",i,sum);

    }

    return 0;

}

Sample output:

Enter the first number of the A.P. series: 1

Enter the total numbers in the A.P. series: 5

Enter the common difference of A.P. series: 3

Sum of the series: 1 + 4 + 7 + 10 + 13 = 35

Definition of arithmetic progression (A.P.):

A series of numbers in which difference of any two consecutive numbers is always a same number that is constant. This constant is called as common difference.

Example of A.P. series:

5 10 15 20 25 …

Here common difference is 5 since difference of any two consecutive numbers for example 20 – 15 or 25 -20 is 5.

Sum of A.P. series:

S_n = n/2(2a + (n-1) d)

T_n term of A.P. series:

T_n = a + (n-1) d