My code

… was written in C++11 and can be compiled with G++, Clang++, Visual C++. You can download it, too. Or just jump to my GitHub repository.

The code contains #ifdefs to switch between the original problem and the Hackerrank version.
Enable #ifdef ORIGINAL to produce the result for the original problem (default setting for most problems).

       
#include <iostream>
       
#include <vector>
       
#include <algorithm>
       
 
       
// ---------- standard prime sieve from my toolbox ----------

       
 
       
// odd prime numbers are marked as "true" in a bitvector

       
std::vector<bool> sieve;
       
 
       
// return true, if x is a prime number

       
bool isPrime(unsigned int x)
       
{
       
  // handle even numbers
       
  if ((x & 1) == 0)
       
    return x == 2;
       
 
       
  // lookup for odd numbers
       
  return sieve[x >> 1];
       
}
       
 
       
// find all prime numbers from 2 to size

       
void fillSieve(unsigned int size)
       
{
       
  // store only odd numbers
       
  const unsigned int half = size >> 1;
       
 
       
  // allocate memory
       
  sieve.resize(half, true);
       
  // 1 is not a prime number
       
  sieve[0] = false;
       
 
       
  // process all relevant prime factors
       
  for (unsigned int i = 1; 2*i*i < half; i++)
       
    // do we have a prime factor ?
       
    if (sieve[i])
       
    {
       
      // mark all its multiples as false
       
      unsigned int current = 3*i+1;
       
      while (current < half)
       
      {
       
        sieve[current] = false;
       
        current += 2*i+1;
       
      }
       
    }
       
}
       
 
       
// ---------- and now problem-specific code ----------

       
 
       
int main()
       
{
       
  // generate all primes
       
  unsigned int limit = 100000000;
       
  unsigned int largestPrime = limit / 2 + 100; // at least one more prime than strictly needed
       
  fillSieve(largestPrime);
       
 
       
  // extract all prime numbers from sieve
       
  std::vector<unsigned int> primes = { 2 };
       
  primes.reserve(3002000); // avoid frequent re-allocations
       
  for (unsigned int i = 3; i < largestPrime; i += 2)
       
    if (isPrime(i))
       
      primes.push_back(i);
       
 
       
#define ORIGINAL
       
#ifndef ORIGINAL
       
  // Hackerrank has several test cases
       
  unsigned int tests = 1;
       
  std::cin >> tests;
       
  while (tests--)
       
#endif
       
  {
       
    std::cin >> limit;
       
 
       
    // compute all products of primes i and j where i <= j
       
    unsigned int count = 0;
       
    for (unsigned int i = 0; primes[i] * primes[i] < limit; i++)
       
      for (unsigned int j = i; primes[i] * primes[j] < limit; j++)
       
        // found one more solutions ...
       
        count++;
       
 
       
    std::cout << count << std::endl;
       
  }
       
 
       
  return 0;
       
}

This solution contains 14 empty lines, 18 comments and 6 preprocessor commands.