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 A216717 #11 Apr 13 2021 10:52:16 %S A216717 1,2,6,24,114,674,4714,37754,340404,3412176,37631268 %N A216717 Duplicate of A174072. %Y A216717 Duplicate of A174072. %K A216717 dead %O A216717 1,2 %A A216717 _N. J. A. Sloane_, Sep 15 2012