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 A216720 #6 Apr 13 2021 17:03:57 %S A216720 2,6,22,109,657,4625,37186,336336,3379058,37328103 %N A216720 Duplicate of A174074. %K A216720 dead %O A216720 3,1