Happy New Year everyone! You probably know what a factorial is. $$n!=n \left(n-1\right)\left(n-2\right)\left(n-3\right)\times3\times2\times1$$ Or, if you like calculus: $$x!=\int_{0}^{\infty} t^x{e^{-t}} dt$$ Like, for example, 8! = 8\(\times\) 7\(\times\)6\(\times\)5\(\times\)4\(\times\)3\(\times\)2\(\times\)1 = 40,320. However, what if we put two exclamation marks? Or a dollar sign? Well today, I am going to show you. Double Factorial The name comes… Continue reading A Super Factorial, Double Factorial, Hyper Factorial?!