// Helper Function, generates factorials function fact(num) { var rval = 1; for (var i = 2; i <= num; i++) rval = rval * i; return rval; } // Calculates number of possible permutations from set n, of length k function permutations(n, k) { var p = fact(n); var v = fact(n-k); return p/v; } console.log( permutations(52, 52) );