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 A151520 #10 Feb 16 2025 08:33:09 %S A151520 1,4,6,21,47,134,323,876,2224,5885,15146,39574,102250,265574,686208, %T A151520 1775646,4583718,11835037,30515520,78652647 %N A151520 Number of 1-sided strip polytans with n cells. %H A151520 Ed Pegg, Jr., <a href="http://demonstrations.wolfram.com/PolyformExplorer/">Illustrations of polyforms</a> %H A151520 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Polytan.html">Polytan</a> %Y A151520 Cf. A006074, A151521. %K A151520 nonn,hard,more %O A151520 1,2 %A A151520 _Ed Pegg Jr_, May 13 2009 %E A151520 a(6)-a(20) from _John Mason_, Jan 07 2022