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 A284767 #6 Apr 05 2020 23:02:41 %S A284767 2,52,720,10120,145822,2134812,31677488,474539092,7162528912, %T A284767 108751977400,1659266548448,25419213710160,390755520225882, %U A284767 6024619021179564,93124153758520074,1442654093474307468 %N A284767 Number of n X 4 0..1 arrays with the number of 1's horizontally or vertically adjacent to some 0 one less than the number of 0's adjacent to some 1. %C A284767 Column 4 of A284771. %H A284767 R. H. Hardin, <a href="/A284767/b284767.txt">Table of n, a(n) for n = 1..173</a> %e A284767 Some solutions for n=4 %e A284767 ..1..1..0..0. .0..0..0..1. .0..1..0..1. .0..0..1..1. .0..1..0..1 %e A284767 ..0..0..0..1. .0..1..0..1. .0..0..1..1. .0..1..0..1. .0..0..1..1 %e A284767 ..1..1..1..1. .0..1..0..1. .0..1..1..1. .0..0..0..0. .1..0..0..1 %e A284767 ..0..0..0..1. .0..1..1..0. .0..0..0..0. .0..1..1..1. .0..1..1..0 %Y A284767 Cf. A284771. %K A284767 nonn %O A284767 1,1 %A A284767 _R. H. Hardin_, Apr 02 2017