Write a C++ program to Calculate the sum of the series (1) + (1+2) + (1+2+3) + (1+2+3+4) + ... + (1+2+3+4+...+n), where n is entered by the user.

Write a C++ program to Calculate the sum of the series (1) + (1+2) + (1+2+3) + (1+2+3+4) + ... + (1+2+3+4+...+n), where n is entered by the user.

Program Code:

#include<iostream>

using namespace std;

int main()

{

int i,j,n;

int sum=0;

cout<<"Enter the value of n for the series : ";

cin>>n;

cout<<endl;

for(i=1;i<=n;i++)

{

for(j=1;j<=i;j++)

{

sum = sum + j;

}

}

cout<<"Sum of the series (1) + (1*2) + (1*2*3) ... + (1+2+3+4+...+n) is : "<<sum;

return 0;

}

The program output is tested on www.jdoodle.com

Output:

Enter the value of n for the series : 15

Sum of the series (1) + (1*2) + (1*2*3) ... + (1+2+3+4+...+n) is : 680

Thanks

Mukesh Rajput