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 A286215 #6 Apr 05 2020 23:28:11 %S A286215 3,3468,123541,30004158,1569283128,380797680269,23594688741164, %T A286215 5201563721481604,366234192215237315,73710966822498902306, %U A286215 5745557094114966956143,1070211615398838835193976 %N A286215 Number of n X 7 0..1 arrays with the number of 1's king-move adjacent to some 0 two less than the number of 0's adjacent to some 1. %C A286215 Column 7 of A286216. %H A286215 R. H. Hardin, <a href="/A286215/b286215.txt">Table of n, a(n) for n = 1..28</a> %e A286215 Some solutions for n=3 %e A286215 ..0..1..0..0..0..1..1. .1..1..0..0..0..0..1. .0..0..1..1..0..0..0 %e A286215 ..1..0..0..0..1..0..0. .0..1..1..0..0..1..1. .1..1..1..0..0..0..1 %e A286215 ..1..1..0..1..1..0..0. .0..0..0..1..0..1..1. .1..1..0..0..1..1..0 %Y A286215 Cf. A286216. %K A286215 nonn %O A286215 1,1 %A A286215 _R. H. Hardin_, May 04 2017