It puts the “!” in probability.

Sometimes it’s good to remember what a factorial is.

In mathematics, the factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n.

10! = 10x9x8x7x6x5x4x3x2x1x = 3,628,800

Factorials show up in a lot of different places especially combinatorials and permutations.

They matter for us in arranging things in a sequence, like the ciphertext letters when trying to break a transposition…

For n letters there are n! ways of arranging them in sequence.  The various ways they are arranged are the permutations.

There’s quite a bit more involved math with factorials but for now this is enough for me.