>>> permutation([1,2,3,5])
[[1, 2, 3, 5], [1, 2, 5, 3], [1, 3, 2, 5], [1, 3, 5, 2], [1, 5, 2, 3], [1, 5, 3, 2], [2, 1, 3, 5], [2, 1, 5, 3], [2, 3, 1, 5], [2, 3, 5, 1], [2, 5, 1, 3], [2, 5, 3, 1], [3, 1, 2, 5], [3, 1, 5, 2], [3, 2, 1, 5], [3, 2, 5, 1], [3, 5, 1, 2], [3, 5, 2, 1], [5, 1, 2, 3], [5, 1, 3, 2], [5, 2, 1, 3], [5, 2, 3, 1], [5, 3, 1, 2], [5, 3, 2, 1]]