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 A336742 #11 Aug 03 2020 03:42:35 %S A336742 1,0,1,1,2,6,17,49,156,520,1762,6110,21713,78469,287393,1065951, %T A336742 3998286,15140500,57817817,222478829,861952579,3360043843,13171307962 %N A336742 Number of self-avoiding cycles of length 2n on the half-Manhattan lattice. %C A336742 In the half-Manhattan lattice, E-W streets run alternately E and W, but N-S streets are two way. %H A336742 Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a336/A336742.java">Java program</a> (github) %Y A336742 Cf. A336724 (self-avoiding walks), A006781 (Manhattan lattice), A006782 (L-lattice), A002931 (square lattice). %K A336742 nonn,walk,more %O A336742 0,5 %A A336742 _Sean A. Irvine_, Aug 02 2020