Numbers can be regarded as product of its factors. For example,
8 = 2 x 2 x 2; = 2 x 4. Write a function that takes an integer n and return all possible combinations of its factors.
Note:
Each combination’s factors must be sorted ascending, for example: The factors of 2 and 6 is [2, 6], not [6, 2].
You may assume that n is always positive.
Factors should be greater than 1 and less than n.
Examples:
input: 1 output: []
input: 37 output: []
input: 12 output: [ [2, 6], [2, 2, 3], [3, 4] ]
input: 32 output: [ [2, 16], [2, 2, 8], [2, 2, 2, 4], [2, 2, 2, 2, 2], [2, 4, 4], [4, 8] ]