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 A057422 #9 Jun 04 2022 19:39:19 %S A057422 0,2,4,12,24,57,112,244,483,998,1979 %N A057422 Axially symmetric (about axis 2) 2n-celled polyominoes with 1 hole. %H A057422 Tomás Oliveira e Silva, <a href="http://sweet.ua.pt/tos/animals.html">Enumeration of polyominoes</a> %Y A057422 Cf. A056880. %K A057422 nonn,more %O A057422 4,2 %A A057422 _N. J. A. Sloane_, Sep 05 2000