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 A026186 #12 Jan 31 2020 08:26:20 %S A026186 1,3,2,7,9,4,5,15,6,19,21,8,25,27,10,11,33,12,13,39,14,43,45,16,17,51, %T A026186 18,55,57,20,61,63,22,23,69,24,73,75,26,79,81,28,29,87,30,31,93,32,97, %U A026186 99,34,35,105,36,37,111,38,115,117,40,41,123 %N A026186 Duplicate of A026136. %K A026186 dead %O A026186 1,2