Hello. So I got task @ university what requires to find all possible combinations from 7 given 2 digit numbers, and that numbers can be flipped around.
Lets say this is numbers: 13 01 02 24 14 12 25
So from all these numbers I need to find all possible combination when numbers flip around, lets say this is couple possible combinations:

13 01 02 24 14 12 25

13 01 02 24 14 12 52

13 01 02 24 14 21 25

13 01 02 24 14 21 52
I tried doing some math how many combinations it would be, and I came up that it would be:
14 * 12 * 10 * 8 * 6 * 4 * 2 = 645 120
P.S. If we use number 13, we can not use him flipped in same combination.
by Mortelity via /r/csharp