Answer:
// Program in C to calculate sum of 1+1.2+.....+1.2.3...n
// include header
#include <stdio.h>
// main function
int main()
{
// variable Declaration and initialization
int n,a,prod=1,sum=0;
// ask to enter the value of n
printf("enter the value of n:");
// read the value of n
scanf("%d",&n);
for(a=1;a<=n;a++)
{
// calculate product
prod=prod*a;
// calculate sum of the series
sum=sum+prod;
}
// print the sum
printf("sum of the series is:%d",sum);
return 0;
}
Explanation:
Read the value of n from user.initialize variables "prod=1" and
"sum=0".Iterate over a for loop to calculate product term as "prod=prod*a".Here prod will have product of all till "a-1" for each "a".Then "a" is multiplied with "prod" and then add to sum.After the loop ends, "sum" will have the total of all the terms.
Output:
enter the value of n:5
sum of the series is:153
