Super !

I sat with my friend to understand the code coz I am not a pro in
coding. Basically, I need to understand the mathematics behind this. I
understood your formula of 9! The formula works because rows and
columns count were same (9).

Lets say, if there were 10 columns and 8 rows and if I wanted to check
how many combinations of 8 numbers are possible, then what would be the
formula to check the count? Just curious...

will it be 8! or 10! ?

Example data

_1 _2 _3 _4 _5 _6 _7 _8 _9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50
51 52 53 54 55 56 57 58 59 60
61 62 63 64 65 66 67 68 69 70
71 72 73 74 75 76 77 78 79 80