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 A274297 #5 Jun 18 2016 09:40:18 %S A274297 1147,2369,2479,2537,2751,3811,3819,5143,5377,5959,6475,6767,7601, %T A274297 7807,8241,9139,9381,9577,10471,11723,11803,12453,12663,12803,12875, %U A274297 13135,14467,15799,16225,16867,17085,17113,17131,18463,19221,19339,19647,19781,19795,21127,21173,21507,22459 %N A274297 a(n) = 2*A090495(n) - 1. %Y A274297 Cf. A090495. %K A274297 nonn %O A274297 1,1 %A A274297 _N. J. A. Sloane_, Jun 18 2016