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 A284215 #7 Apr 05 2020 22:41:25 %S A284215 1,6,70,6511,2417194,3945536189,26772321109067,749608559151363940, %T A284215 85781667864838421304454,39910247433142071128719168435, %U A284215 75224282551539452957156354090109083 %N A284215 Number of n 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 A284215 Diagonal of A284222. %H A284215 R. H. Hardin, <a href="/A284215/b284215.txt">Table of n, a(n) for n = 1..12</a> %e A284215 Some solutions for n=4 %e A284215 ..0..1..0..1. .0..1..1..0. .0..1..1..0. .0..1..1..0. .0..1..1..1 %e A284215 ..0..1..1..1. .1..0..1..1. .0..1..0..1. .0..1..1..1. .0..0..1..0 %e A284215 ..0..1..1..1. .1..0..0..0. .1..0..1..0. .0..1..1..0. .0..1..0..1 %e A284215 ..0..0..1..1. .0..1..1..0. .0..1..1..0. .0..1..0..0. .1..1..1..0 %Y A284215 Cf. A284222. %K A284215 nonn %O A284215 1,2 %A A284215 _R. H. Hardin_, Mar 23 2017