My code

… was written in C++ and can be compiled with G++, Clang++, Visual C++. You can download it, too. Or just jump to my GitHub repository.

       
#include <iostream>
       
 
       
int main()
       
{
       
  unsigned int tests;
       
  std::cin >> tests;
       
  while (tests--)
       
  {
       
    unsigned long long x;
       
    std::cin >> x;
       
 
       
    unsigned long long sum        = 0; // 1   + 2   + ...
       
    unsigned long long sumSquared = 0; // 1^2 + 2^2 + ...
       
 
       
    for (unsigned long long i = 1; i <= x; i++)
       
    {
       
      sum        += i;
       
      sumSquared += i*i;
       
    }
       
    // chances are that your compiler (partially) unrolls this simple loop
       
 
       
    // actually we don't need a loop for the sum (and the sum of squares)
       
    // => see "Alternative" section above
       
 
       
    // we had (1+2+...) instead of (1+2+...)^2
       
    unsigned long long squaredSum = sum * sum;
       
    std::cout << (squaredSum - sumSquared) << std::endl;
       
  }
       
  return 0;
       
}

This solution contains 5 empty lines, 4 comments and 1 preprocessor command.