permutation.js

function permutation(n) { 
  if(n == 0 || n == 1) return 1;
  if(f[n] > 0) return f[n];
  //console.log(n);
  return f[n] = factorial(n-1) * n;
}

function permutation(n) {
	var p = 1;
	while ( n != 1 ) {
	    p *= n
	    n--
	}

	return p
}