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 A307456 #12 Apr 22 2019 11:46:36 %S A307456 2,2,1,4,11,24,47,99,211,437,909,1925 %N A307456 a(n) is the number of canonical polygons with 2n edges having exactly 2 lines of reflection symmetry. %H A307456 Lars Blomberg, <a href="/A307456/a307456.pdf">Examples of canonical polygons with exactly 2 lines of reflection symmetry</a> %Y A307456 Cf. A052436, A307387, A307391, A307426, A307454, A307455, A307456, A307519. %K A307456 nonn,more %O A307456 2,1 %A A307456 _Lars Blomberg_, Apr 09 2019