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 A316194 #16 Jan 08 2019 19:08:57 %S A316194 0,1,1,3,4,16,23,87 %N A316194 Number of symmetric self-avoiding polygons on square lattice with perimeter 2*n, not counting rotations and reflections as distinct. %C A316194 The sequence includes polygons of 2-fold, i.e., mirror or rotational, and higher (order >= 4) symmetry. %H A316194 Hugo Pfoertner, <a href="http://www.randomwalk.de/sequences/a316194.htm">Illustration of polygons of perimeter <= 16</a>. %Y A316194 Cf. A002931, A266549, A316196, A323188, A323189. %K A316194 nonn,walk,more %O A316194 1,4 %A A316194 _Hugo Pfoertner_, Jun 27 2018