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 A172997 #14 Mar 30 2012 18:52:39 %S A172997 1,5,6,8,34,131 %N A172997 Numbers n such that for p=prime(n), (2p-1)^(2p-1) mod 2^(2p-1) is prime. %e A172997 5 is in the sequence, since prime(5)=11 and (2*11-1)^(2*11-1) mod 2^(2*11-1) = 21^21 mod 2^21 = 1472837 is prime. %Y A172997 Cf. A000040, A000079, A000312, A178537, A178966. %K A172997 nonn %O A172997 1,2 %A A172997 _Juri-Stepan Gerasimov_, Jan 01 2011