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 A237432 #24 Jun 30 2023 10:33:13 %S A237432 0,1,102,255359,15504309761,21955745395591600, %T A237432 712319733455900182066337,524246290066954425217045809870657 %N A237432 Number of nonisomorphic Hamiltonian cycles on (4n-2) X (4n-2) square grid of points with four-fold rotational symmetry (and no other symmetry). %C A237432 For square grids of m X m points, there are solutions only for m = (4n-2). %H A237432 Ed Wynn, <a href="http://arxiv.org/abs/1402.0545">Enumeration of nonisomorphic Hamiltonian cycles on square grid graphs</a>, arXiv:1402.0545 [math.CO], 2014. %F A237432 a(n) = A238819(n-1) / 2 for n > 1. - _Andrew Howroyd_, Apr 06 2016 %e A237432 The two cycles counted as a single class for n=2. These are isomorphic (here meaning isomorphic under the full symmetry group of the square), since each is a reflection of the other. %e A237432 o-o o-o-o-o o-o-o-o o-o %e A237432 | | | | | | | | %e A237432 o o o o-o-o o-o-o o o o %e A237432 | | | | | | | | %e A237432 o o-o o-o-o o-o-o o-o o %e A237432 | | | | %e A237432 o-o-o o-o o o o-o o-o-o %e A237432 | | | | | | | | %e A237432 o-o-o o o o o o o o-o-o %e A237432 | | | | | | | | %e A237432 o-o-o-o o-o o-o o-o-o-o %Y A237432 Cf. A209077, A227005, A237431. %K A237432 nonn,walk,hard,more %O A237432 1,3 %A A237432 _Ed Wynn_, Feb 07 2014 %E A237432 a(6)-a(8) from _Andrew Howroyd_, Apr 06 2016