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 A331986 #40 Feb 16 2025 08:33:59 %S A331986 1,4,8,84,56,136,52,216,16,1504,2352,1152,1344,123216,82432,11008, %T A331986 308992 %N A331986 Number of snake-like polyominoes with the maximum possible number of unit squares in an n X n square. %C A331986 The maximum possible number of unit squares is given by A331968(n). %C A331986 Equivalently, a(n) is the number of maximum length paths without chords in the n X n grid graph. A path without chords is an induced subgraph that is a path. %C A331986 For n > 1, a(n) is a multiple of 4 since a solution can have at most one symmetry considering rotations and reflections. - _Andrew Howroyd_, Feb 04 2020 %H A331986 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GridGraph.html">Grid Graph</a> %e A331986 For n = 4 the number of snake-like polyominoes with 11 cells is 84. %Y A331986 Main diagonal of A360916. %Y A331986 Cf. A331968, A059525 (connected induced subgraphs), A099155. %Y A331986 Cf. A332920 (non-isomorphic snakes), A332921 (symmetric snakes). %K A331986 nonn,walk,hard,more %O A331986 1,2 %A A331986 _Alain Goupil_, Feb 03 2020 %E A331986 a(15) from _Andrew Howroyd_, Feb 04 2020 %E A331986 a(16)-a(17) from _Yi Yang_, Oct 03 2022