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 A286975 #6 Apr 05 2020 23:29:16 %S A286975 0,30,538,8270,123706,1853532,27938670,424161696,6473516290, %T A286975 99212813068,1525788269640,23533226594814,363874149524074, %U A286975 5638501690692214,87539755014915366,1361389260565705844,21203931694258697402 %N A286975 Number of n X 4 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. %C A286975 Column 4 of A286979. %H A286975 R. H. Hardin, <a href="/A286975/b286975.txt">Table of n, a(n) for n = 1..174</a> %e A286975 Some solutions for n=4 %e A286975 ..0..1..1..1. .0..0..1..0. .1..1..0..0. .1..0..0..0. .0..1..0..1 %e A286975 ..0..0..0..1. .1..0..1..0. .0..0..1..0. .1..0..1..0. .0..0..0..1 %e A286975 ..1..0..0..1. .1..0..0..0. .1..1..0..1. .0..1..0..1. .1..0..0..0 %e A286975 ..0..0..1..1. .1..1..1..0. .0..0..0..0. .1..0..0..0. .0..1..1..1 %Y A286975 Cf. A286979. %K A286975 nonn %O A286975 1,2 %A A286975 _R. H. Hardin_, May 17 2017