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 A237431 #24 Jun 30 2023 10:20:21 %S A237431 0,1,3,20,244,6891,378813,47917598,12118420172,6998287399637 %N A237431 Number of nonisomorphic Hamiltonian cycles on 2n X 2n square grid of points with exactly two axes of reflective symmetry. %H A237431 Ed Wynn, <a href="https://arxiv.org/abs/1402.0545">Enumeration of nonisomorphic Hamiltonian cycles on square grid graphs</a>, arXiv:1402.0545 [math.CO], 2014. %e A237431 Examples of 2 of the 3 classes for n=3. Note that all examples also have two-fold (but not four-fold) rotational symmetry. %e A237431 o-o-o-o-o-o o-o-o-o-o-o %e A237431 | | | | %e A237431 o-o-o o-o-o o o-o o-o o %e A237431 | | | | | | | | %e A237431 o-o-o o-o-o o-o o o o-o %e A237431 | | | | %e A237431 o-o-o o-o-o o-o o o o-o %e A237431 | | | | | | | | %e A237431 o-o-o o-o-o o o-o o-o o %e A237431 | | | | %e A237431 o-o-o-o-o-o o-o-o-o-o-o %Y A237431 Cf. A209077, A227005, A237432. %K A237431 nonn,walk,more %O A237431 1,3 %A A237431 _Ed Wynn_, Feb 07 2014