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 A284218 #6 Apr 05 2020 22:43:28 %S A284218 6,44,499,6511,91260,1317770,19371893,288303232,4330336770, %T A284218 65507133232,996599090507,15232184395483,233708530421124, %U A284218 3597476814925298,55530194727444557,859222993580853779,13322830756899018309 %N A284218 Number of n X 4 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 A284218 Column 4 of A284222. %H A284218 R. H. Hardin, <a href="/A284218/b284218.txt">Table of n, a(n) for n = 1..210</a> %e A284218 Some solutions for n=4 %e A284218 ..0..0..0..1. .0..1..1..0. .0..1..0..0. .0..0..1..0. .0..0..1..1 %e A284218 ..0..1..1..0. .1..1..0..0. .1..1..1..1. .0..0..0..1. .0..0..1..0 %e A284218 ..1..1..1..1. .0..1..1..0. .0..0..0..1. .1..1..0..1. .0..1..1..0 %e A284218 ..0..0..0..0. .0..1..1..1. .1..0..1..1. .0..1..0..1. .1..1..1..1 %Y A284218 Cf. A284222. %K A284218 nonn %O A284218 1,1 %A A284218 _R. H. Hardin_, Mar 23 2017