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 A286973 #11 Sep 02 2025 11:46:54 %S A286973 0,0,5,30,126,520,2088,8192,32083,125728,492331,1927334,7545086, %T A286973 29542032,115713230,453479812,1778221568,6976989468,27390464896, %U A286973 107590106636,422842742731,1662688326476,6541232413273,25746371202362,101384373381977,399406874608396,1574130883669277 %N A286973 Number of n X 2 0..1 arrays with the number of 1's horizontally or vertically adjacent to some 0 two less than the number of 0's adjacent to some 1. %H A286973 R. H. Hardin, <a href="/A286973/b286973.txt">Table of n, a(n) for n = 1..210</a> %e A286973 Some solutions for n=4: %e A286973 ..0..0. .0..1. .1..0. .0..1. .0..0. .0..0. .1..0. .0..0. .0..0. .0..1 %e A286973 ..1..0. .0..0. .0..0. .0..1. .1..1. .0..1. .1..0. .0..1. .1..0. .0..0 %e A286973 ..1..0. .0..0. .0..1. .0..0. .0..0. .0..1. .0..0. .0..0. .0..1. .1..1 %e A286973 ..0..0. .1..0. .1..0. .1..0. .0..0. .0..0. .0..1. .0..1. .0..0. .0..0 %Y A286973 Column 2 of A286979. %K A286973 nonn,changed %O A286973 1,3 %A A286973 _R. H. Hardin_, May 17 2017