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 A284224 #6 Apr 05 2020 22:47:27 %S A284224 4,19,70,499,3214,22729,163708,1209005,9018250,67956917,515031078, %T A284224 3926103884,30049105764,230871573750,1779036977175,13746097605518, %U A284224 106448904000193,826010061981163,6420762665883318,49989175241774203 %N A284224 Number of 3 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 A284224 Row 3 of A284222. %H A284224 R. H. Hardin, <a href="/A284224/b284224.txt">Table of n, a(n) for n = 1..210</a> %e A284224 Some solutions for n=4 %e A284224 ..0..1..0..1. .0..0..1..1. .0..0..0..1. .0..1..1..0. .0..0..0..1 %e A284224 ..0..0..1..1. .0..0..0..1. .0..1..1..1. .0..1..1..0. .1..0..1..1 %e A284224 ..1..0..0..1. .0..0..0..1. .1..1..1..1. .0..1..0..1. .0..0..1..1 %Y A284224 Cf. A284222. %K A284224 nonn %O A284224 1,1 %A A284224 _R. H. Hardin_, Mar 23 2017