function decomp(n){
  var primeFactors = [];
  var fact = 1;

  for (var i = 2; i <= n; i++) {
     fact = fact * i;
  }

  while (fact % 2 === 0) {
    primeFactors.push(2);
    fact = fact/2;
  }

  var sqrtFact = Math.sqrt(fact);
    for (var i = 2; i <= sqrtFact; i++) {
    while (fact % i === 0) {
      primeFactors.push(i);
      fact = fact/i;
      }
  }

  if (fact > 2) {
    primeFactors.push(fact);
  }
   return primeFactors;
}