title: Hexagonal Number
signature: function hexagonalNumber($n) {
test_code: <?php
  
  
  // SOLUTION CODE 
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE 
  // ============================================
  function validateSolution($actual, $expected){
      return serialize($actual) == serialize($expected);
  }
  
  function driver($n, $expected){
      try{
        if (validateSolution(PLACEHOLDER_FN_NAME($n), $expected)){
          return "PASSED";
        }
        return "FAILED";
      }
      catch (Exception $exception_obj) {
        return get_class($exception_obj);
      }
  }
  
  function main(){
      printf("TEST-0...%s\n",driver(
        38, 
        2850));
      
      printf("TEST-1...%s\n",driver(
        44, 
        3828));
      
      printf("TEST-2...%s\n",driver(
        58, 
        6670));
      
      printf("TEST-3...%s\n",driver(
        10, 
        190));
      
      printf("TEST-4...%s\n",driver(
        31, 
        1891));
      
      printf("TEST-5...%s\n",driver(
        53, 
        5565));
      
      printf("TEST-6...%s\n",driver(
        94, 
        17578));
      
      printf("TEST-7...%s\n",driver(
        64, 
        8128));
      
      printf("TEST-8...%s\n",driver(
        71, 
        10011));
      
      printf("TEST-9...%s\n",driver(
        59, 
        6903));
      
  }
  
  main();
  ?>
source_py: def hexagonal_number(n):
      return (n * ((2 * n) - 1))
source_cpp: int hexagonal_number(int n) {
    return n * ( 2 * n - 1 );
  }