Thread:John Lee Gamma Guild Team Vi Hart/@comment-25079450-20150912213139/@comment-27766450-20160218181252

Bird2525 wrote: Is there such a thing as negative factorials? To expand on Jabbar's answer, n! = n*(n-1)!, for example 4! = 4*3! = 4*6 = 24.

If you reformulate this formula you get: (n-1)! = n! / n, if n=1 you get, 0! = 1!/ 1 = 1,

and if n=0 you get (-1)!=0! / 0 = 1 / 0 = UNDEFINED, so the negative factorials is the same as deviding by zero, but it is possible to compute the factorial for negative fractions (try (-1/2)! using WolframAlpha: http://www.wolframalpha.com/input/?i=(-1%2F2)!)