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 A342963 #19 May 20 2025 08:52:06 %S A342963 1,2,15,110,1051,10636,113290,1234189,13674761,153289285 %N A342963 a(n) is the number of sticky polyhexes with 2*n cells. %C A342963 A sticky polyhex is defined as follows: %C A342963 - A single dihex (polyhex of size 2) is a sticky polyhex. %C A342963 - If a polyhex X is sticky, X plus a dihex Y is also sticky if X and Y share at least two unit sides. %C A342963 - Any polyhex that cannot be formed by the above definition is not sticky. %C A342963 This sequence counts free polyhexes; two polyhexes which are equivalent under reflection and/or rotation are counted only once. %C A342963 a(n) < A000228(2n) for n > 1. %H A342963 Woosuk Kwak, <a href="https://codegolf.stackexchange.com/questions/222709/sticky-polyhexes">Sticky Polyhexes</a>, Code Golf Stack Exchange. %e A342963 The two sticky tetrahexes are: %e A342963 * * * * * %e A342963 * * * %e A342963 The following is the full list of 15 sticky hexahexes (polyhexes of size 6): %e A342963 * * * * * * * * * * * * * * %e A342963 * * * * * * * * * * * * * %e A342963 * * * %e A342963 --- %e A342963 * * * * * * * * * * %e A342963 * * * * * * * * * * * * * * * %e A342963 * * * * * %e A342963 --- %e A342963 * * * * * * * * * * * * * * * * %e A342963 * * * * * * * * * * %e A342963 * * * * %Y A342963 Cf. A000228. %K A342963 nonn,hard,more %O A342963 1,2 %A A342963 _Woosuk Kwak_, Mar 31 2021