A Super Factorial, Double Factorial, Hyper Factorial?!

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?!