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 A284223 #6 Apr 05 2020 22:46:44 %S A284223 2,6,13,44,143,495,1746,6399,23776,89321,337909,1285710,4914573, %T A284223 18861581,72633154,280492954,1085801918,4211904917,16367963509, %U A284223 63710308355,248341387058,969279971828,3787525164193,14815659532381,58010290470976 %N A284223 Number of 2 X n 0..1 arrays with the number of 1's horizontally or antidiagonally adjacent to some 0 equal to the number of 0's adjacent to some 1, with top left element zero. %C A284223 Row 2 of A284222. %H A284223 R. H. Hardin, <a href="/A284223/b284223.txt">Table of n, a(n) for n = 1..210</a> %e A284223 Some solutions for n=4 %e A284223 ..0..0..1..1. .0..0..1..0. .0..0..0..0. .0..0..0..1. .0..0..0..1 %e A284223 ..1..0..0..0. .1..1..0..0. .1..1..0..1. .1..1..0..0. .1..0..1..1 %Y A284223 Cf. A284222. %K A284223 nonn %O A284223 1,1 %A A284223 _R. H. Hardin_, Mar 23 2017