  What is the number of rolls of fair 6-sided dice until the first time the
total sum of all rolls is a prime? We compute the expectation and the variance
of this random variable up to an additive error of less than 10^{-4}. This is a
solution to a puzzle suggested by DasGupta (2017) in the Bulletin of the
Institute of Mathematical Statistics, where the published solution is
incomplete. The proof is simple, combining a basic dynamic programming
algorithm with a quick Matlab computation and basic facts about the
distribution of primes.
