a(n) = smallest number k such that p(n)*k+1 is prime, where p(n) is the n-th prime.
1, 2, 2, 4, 2, 4, 6, 10, 2, 2, 10, 4, 2, 4, 6, 2, 12, 6, 4, 8, 4, 4, 2, 2, 4, 6, 6, 6, 10, 2, 4, 2
2 seqfan posts
Thu Oct 20 22:13:34 CEST 2011 [seqfan] Re: Smallest prime of form k*p(n) + 1