N is a positive integer. If you list the positive integers in rows of N such that the first row contains 1 to N, the second row contains N+1 to 2*N, and so on, then the first row with no prime is immediately followed by another row with no prime. What is N?
(In reply to
re(4): My solution by Jer)
I wasn't attempting a proof: just trying to answer Ady's question to Math Man, of Why would one think there are no others. One's intuition is that this is the case. Of course intuition can be wrong, but there are reasons for having a given intuition.

Posted by Charlie
on 20160801 07:57:10 