0! and 0^0
1! = 1 2! = 1 * 2 3! = 1 * 2 * 3 etc So how would we decide what 0! should be? Reverse the process. 3! = 6 2! = 3!/3 = 6/3 = 2 1! = 2!/2 = 2/1 = 1 0! = 1!/1 = 1/1 = 1 (-1)! = 0!/0 = 1/0. oops. (-1)! does not exist. thus (-2)! does not exist. etc We can find a factorial for all numbers except for the... Sign in to see full entry.