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 A289647 #6 Apr 05 2020 23:33:08 %S A289647 0,44,607,8554,121162,1756800,25760875,382162921,5717697619, %T A289647 86172849366,1306560879457,19912006342895,304785181627320, %U A289647 4682731916448540,72178508386597722,1115665066715856620,17287052005230219381 %N A289647 Number of n X 4 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 A289647 Column 4 of A289651. %H A289647 R. H. Hardin, <a href="/A289647/b289647.txt">Table of n, a(n) for n = 1..210</a> %e A289647 Some solutions for n=4 %e A289647 ..1..0..1..1. .1..0..1..0. .0..0..1..1. .1..1..0..1. .1..0..1..1 %e A289647 ..0..0..1..1. .1..0..0..1. .0..1..0..0. .0..0..0..1. .0..0..1..0 %e A289647 ..0..0..1..0. .0..0..0..1. .0..1..1..0. .0..0..0..0. .0..0..0..1 %e A289647 ..1..0..0..0. .0..1..1..0. .1..0..0..0. .0..0..0..1. .1..0..0..1 %Y A289647 Cf. A289651. %K A289647 nonn %O A289647 1,2 %A A289647 _R. H. Hardin_, Jul 09 2017