7. Let $Q_{n}=p_{1} p_{2} \cdots p_{n}+1$ where $p_{1}, p_{2}, \ldots, p_{n}$ are the $n$ smallest primes. Determine the smallest prime factor of $Q_{n}$ for $n=1,2,3,4,5$, and 6 . Do you think $Q_{n}$ is prime infinitely often? (This is an unresolved question.)
7. $3,7,31,211,2311,59$