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 A007669 M1135 #13 Nov 27 2017 23:08:19 %S A007669 1,2,4,8,16,36,80,194,506,1449,4631,17106,74820,404283,2815595 %N A007669 Duplicate of A034343. %K A007669 dead %O A007669 1,2