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 A289646 #6 Apr 05 2020 23:32:17 %S A289646 0,11,61,607,3160,31271,183390,1714758,10957160,97430209,660963859, %T A289646 5659723958,40059954256,334030499016,2436982696260,19950172380212, %U A289646 148739597215073,1202453728957318,9105730676248720,72992556634640541 %N A289646 Number of n X 3 0..1 arrays with the number of 1's horizontally, antidiagonally or vertically adjacent to some 0 two less than the number of 0's adjacent to some 1. %C A289646 Column 3 of A289651. %H A289646 R. H. Hardin, <a href="/A289646/b289646.txt">Table of n, a(n) for n = 1..210</a> %e A289646 Some solutions for n=4 %e A289646 ..1..0..0. .0..0..0. .1..0..0. .0..1..1. .1..0..0. .0..0..1. .0..1..1 %e A289646 ..0..0..1. .0..0..0. .0..1..0. .0..1..0. .0..0..1. .0..1..1. .0..0..0 %e A289646 ..0..0..1. .0..1..0. .0..1..1. .0..0..0. .0..1..1. .0..0..0. .0..1..0 %e A289646 ..1..0..1. .1..1..0. .0..1..0. .1..1..0. .1..0..0. .0..0..0. .1..1..0 %Y A289646 Cf. A289651. %K A289646 nonn %O A289646 1,2 %A A289646 _R. H. Hardin_, Jul 09 2017