Originally Posted by

**browni3141** I wouldn't even bother with using Wilson's Theorom for practical purposes. It's interesting to study, but it's probably faster to check each prime up to sqrt(n) as a divisor of n, n being the number you are testing. This is probably the easiest method to write a program for. There are prime generating polynomials, but they aren't perfect. This one discovered by Euler is considered best:

x*x - x + 41

I'm pretty sure that there is no formula like the one you are asking for though.