1. The problem statement, all variables and given/known data Why does (p*q+2)-(p+q) always give a prime number when p and q are prime? Is there a similar formula that would prove this 2. Relevant equations That's what I'm looking for. It might have something to do with Eulers formula 3. The attempt at a solution I tried to find online a formula that would justify this, but was unable to find anything.