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 A237430 #13 Jun 30 2023 10:26:01 %S A237430 0,0,5,366,129871,174041330,1343294003351,41725919954578785, %T A237430 7159149948562719664049,5065741493544986113047994120 %N A237430 Number of nonisomorphic Hamiltonian cycles on 2n X 2n square grid of points with two-fold rotational symmetry (and no other symmetry). %H A237430 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 A237430 a(n) = A227257(n) - A237429(n). %e A237430 An example of each isomorphism class for n=3. %e A237430 o-o-o-o-o-o o-o-o-o-o-o o-o-o-o-o-o o-o-o-o o-o o-o-o-o o-o %e A237430 | | | | | | | | | | | | | | %e A237430 o-o-o-o o-o o o-o-o-o-o o o-o o-o-o o-o o-o o o o o-o o-o o %e A237430 | | | | | | | | | | | | | | | | %e A237430 o-o-o-o o-o o o-o-o-o-o o o o o o-o o-o o-o-o o o-o o o-o-o %e A237430 | | | | | | | | | | | | | | %e A237430 o-o o-o-o-o o-o-o-o-o o o-o o o o o o o-o-o o-o o-o-o o o-o %e A237430 | | | | | | | | | | | | | | | | %e A237430 o-o o-o-o-o o-o-o-o-o o o-o-o o-o o o o o-o o-o o o-o o-o o %e A237430 | | | | | | | | | | | | | | %e A237430 o-o-o-o-o-o o-o-o-o-o-o o-o-o-o-o-o o-o o-o-o-o o-o o-o-o-o %Y A237430 Cf. A209077, A227257, A237429. %K A237430 nonn,walk,more %O A237430 1,3 %A A237430 _Ed Wynn_, Feb 07 2014