Challenge for you...

[mnrvovrfc]

Are we now talking about prime numbers, or about the factorial? 

The challenge was to compute the prime numbers involving factorial because it was in a formula that was presented in the first post. Petr presented code which doesn't conform but does produce the first 100 primes.

Here is 500! curtesy of bplus string math

Involve the "string math" into the formula presented in the first post, because that's the challenge.