# Program to calculate the series (1) + (1+2) + (1+2+3) + &#8230; + (1+2+3+4+&#8230;+n) in C++

## C++ Program to calculate the series (1) + (1+2) + (1+2+3) + (1+2+3+4) + … + (1+2+3+4+…+n)

Given: The value of n is input from user and we find the sum of the series where i-th term is sum of first i natural numbers.

Example:

Input : n = 6

Output :

1 = 1

1 + 2 = 3

1 + 2 + 3 = 6

1 + 2 + 3 + 4 = 10

1 + 2 + 3 + 4 + 5 = 15

1 + 2 + 3 + 4 + 5 + 6 = 21

The sum of the above series is : 56

### # Algorithm

1. Take input n from the user.
2. Start loops starting from 1 to n and calculate sum for each iteration.
3. And print the total sum as output.

### Code:

//C++ program to find the sum of the series (1)+(1+2)+(1+2+3)+(1+2+3+...+n)
#include <iostream>
using namespace std;
int main()
{
int i, j, n, sum, total = 0;
cout << "Enter the value for nth term: ";
cin >> n;
for (i = 1; i <= n; i++)
{
sum = 0;

for (j = 1; j &lt;= i; j++)

{

total += j;

sum += j;

cout &lt;&lt; j;

if (j &lt; i)

{

cout &lt;&lt; "+";

}

}

cout &lt;&lt; " = " &lt;&lt; sum &lt;&lt; endl;

}
cout << "\nThe sum of the above series is: " << total << endl;
}