# C++ Program to Calculate Sum of Series 1²+2²+3²+n²

Write a C++ Program to Calculate Sum of Series 1²+2²+3²+n² with an example. The math formula to find Sum of Series 1²+2²+3²+…+n² = n(n + 1)(2n + 1)/6.

```#include<iostream>

using namespace std;

int main()
{
int number, sum = 0;

cout << "Please Enter the Number to find sum of Series 1^2 + 2^2 =  ";
cin >> number;

sum = (number * (number + 1) * (2 * number + 1 )) / 6;

cout << "\nThe Sum of the Series of " << number << " number = " << sum ;

return 0;
}```
``````Please Enter the Number to find sum of Series 1^2 + 2^2 =  10

The Sum of the Series of 10 number = 385``````

This below shown the C++ Program to Calculate Sum of Series 1²+2²+3²+n² is the same as the above. Here, we used C++ for loop to display the 1²+2²+3²+n² series as an output.

```#include<iostream>

using namespace std;

int main()
{
int number, sum = 0;

cout << "Please Enter the Number to find sum of Series 1^2 + 2^2 =  ";
cin >> number;

sum = (number * (number + 1) * (2 * number + 1 )) / 6;

cout << "\nThe Sum of the Series of " << number << " number = " << sum << "\n\n";

for(int i = 1; i <= number; i++)
{
if (i != number)
cout << i << "^2 + ";
else
cout << i << "^2 = " << sum;
}

return 0;
}```

## C++ Program to Calculate Sum of Series 1²+2²+3²+n² using Functions

```#include<iostream>

using namespace std;

void sumOfSeries (int number)
{
int sum = 0;

sum = (number * (number + 1) * (2 * number + 1 )) / 6;

cout << "\nThe Sum of the Series of " << number << " number = " << sum << "\n\n";

for(int i = 1; i <= number; i++)
{
if (i != number)
cout << i << "^2 + ";
else
cout << i << "^2 = " << sum;
}
}
int main()
{
int number;

cout << "Please Enter the Number to find sum of Series 1^2 + 2^2 =  ";
cin >> number;

sumOfSeries (number);

return 0;
}```
``````Please Enter the Number to find sum of Series 1^2 + 2^2 =  20

The Sum of the Series of 20 number = 2870

1^2 + 2^2 + 3^2 + 4^2 + 5^2 + 6^2 + 7^2 + 8^2 + 9^2 + 10^2 + 11^2 + 12^2 + 13^2 + 14^2 + 15^2 + 16^2 + 17^2 + 18^2 + 19^2 + 20^2 = 2870``````