This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A236465 #10 Jan 27 2014 22:09:42 %S A236465 2,2,3,3,2,13,2,11,19,2,2,5,11,2,31,53,3,31,43,19,13,11,43,23,7,5,13, %T A236465 5,29,2,29,17,53,157,13,13,3,5,127,7,97,5,97,2,89,61,7,71,61,5,127, %U A236465 113,37,191,107,17,197,37,101,2,5,7,17,457,3,19,29,103,227 %N A236465 Smallest prime a(n) such that 1 + a(1)*a(2)*...*a(n) is prime. %H A236465 Giovanni Resta, <a href="/A236465/b236465.txt">Table of n, a(n) for n = 1..500</a> %e A236465 a(1) = 2 because 1 + 2 = 3, which is prime. %e A236465 a(2) = 2 because 1 + 2 * 2 = 5, which is prime. %e A236465 a(3) = 3 because 2 doesn't work, since 1 + 2 * 2 * 2 = 9 = 3^2, but 3 does work, giving 1 + 2 * 2 * 3 = 13, which is prime. %t A236465 pr = 1; Table[p = 2; While[! PrimeQ[p * pr + 1], p = NextPrime@p]; pr *= p; p, {n, 100}] (* _Giovanni Resta_, Jan 26 2014 *) %Y A236465 Cf. A036012, A039726. %K A236465 nonn %O A236465 1,1 %A A236465 _Thomas Ordowski_, Jan 26 2014 %E A236465 a(11)-a(69) from _Giovanni Resta_, Jan 26 2014