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 A215449 #21 Sep 24 2021 13:43:16 %S A215449 5,10,17,29,51,90 %N A215449 Duplicate of A259967. %K A215449 dead %O A215449 3,1 %A A215449 _Jonathan Vos Post_, Aug 10 2012