I think this one is a tough one, so I gave up trying after a couple of days.
I hope you guys can help me.
Let’s say I got an array of x elements: [1,2,3,…,x]
What I want is the combinations of (x-1), (x-2), …, 2 elements.
e.g. If x = 4, I want the following combinations:
123
124
134
234
(combinations of 3 elements)
12
13
14
23
24
34
(combinations of 2 elements)
Thanks all in advance! 
