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 A307426 #17 Apr 22 2019 11:46:48 %S A307426 2,2,7,22,79,289,1145,4655,19314,81242,345785,1484065,6414999,27895652 %N A307426 a(n) is the number of canonical polygons with 4n edges having 4-fold rotational symmetry. %H A307426 Lars Blomberg, <a href="/A307426/a307426.pdf">Examples of canonical polygons with 4-fold rotational symmetry</a> %Y A307426 Cf. A052436, A307387, A307391, A307426, A307454, A307455, A307456, A307519. %K A307426 nonn,more %O A307426 1,1 %A A307426 _Lars Blomberg_, Apr 08 2019