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 A057425 #9 Jun 04 2022 19:39:42 %S A057425 1,7,42,193,853,3553,14564,58636,234523 %N A057425 Number of rotationally symmetric 2n-celled polyominoes with 1 hole. %H A057425 Tomás Oliveira e Silva, <a href="http://sweet.ua.pt/tos/animals.html">Enumeration of polyominoes</a> %Y A057425 Cf. A056883. %K A057425 nonn,more %O A057425 5,2 %A A057425 _N. J. A. Sloane_, Sep 05 2000