Consider the product of primes Pn=p1p2…pnP_n = p_1 p_2 \dots p_nPn=p1p2…pn. What can be said about Pn+1P_n + 1Pn+1?
It is always a prime number.
It is always a power of 2.
It is never divisible by any prime p≤pnp \leq p_np≤pn.
It is always a perfect square.