Wikipedia talks about exactly what you want.
Mills' constant - Wikipedia, the free encyclopedia
Consider the number theta
(i.e. Mills Constant), so that p(n) = [ (theta)^(3^n) ] is prime for all n in N, where [ ] denotes the integer part symbol, and n is a natural number.
Find theta (Mills' Constant) to 10 decimal places, show your working.
Determine which primes are values p_n