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 A284217 #6 Apr 05 2020 22:42:44 %S A284217 3,13,70,467,3224,23218,170155,1264605,9488108,71718240,545264052, %T A284217 4165262662,31943452900,245786167555,1896529843618,14669730799547, %U A284217 113713016901442,883107039574428,6869733556332042,53519589494550372 %N A284217 Number of n X 3 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 A284217 Column 3 of A284222. %H A284217 R. H. Hardin, <a href="/A284217/b284217.txt">Table of n, a(n) for n = 1..210</a> %e A284217 Some solutions for n=4 %e A284217 ..0..1..0. .0..0..1. .0..0..1. .0..1..0. .0..0..1. .0..1..0. .0..0..0 %e A284217 ..1..0..1. .0..1..1. .0..0..1. .1..0..1. .0..1..0. .1..0..1. .0..1..1 %e A284217 ..1..1..0. .0..1..1. .1..1..0. .0..1..1. .1..1..1. .0..0..0. .1..1..0 %e A284217 ..0..1..0. .1..1..1. .0..0..1. .0..1..1. .1..1..1. .1..1..1. .1..0..1 %Y A284217 Cf. A284222. %K A284217 nonn %O A284217 1,1 %A A284217 _R. H. Hardin_, Mar 23 2017