**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**

- Take input n from the user.
- Start loops starting from 1 to n and calculate sum for each iteration.
- 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 <= i; j++)
{
total += j;
sum += j;
cout << j;
if (j < i)
{
cout << "+";
}
}
cout << " = " << sum << endl;
}
cout << "\nThe sum of the above series is: " << total << endl;
}
```

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