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 A284450 #6 Apr 05 2020 22:58:41 %S A284450 1,0,102,250,5253,16478,278315,1019120,15188955,62846854,850526529, %T A284450 3891052774,48586797398,241642747938,2818541243728,15034216343154, %U A284450 165507316465985,936470483789652,9815405179117090,58379693308010828 %N A284450 Number of n X 3 0..1 arrays with the number of 1's king-move adjacent to some 0 one less than the number of 0's adjacent to some 1. %C A284450 Column 3 of A284455. %H A284450 R. H. Hardin, <a href="/A284450/b284450.txt">Table of n, a(n) for n = 1..210</a> %e A284450 Some solutions for n=4 %e A284450 ..0..0..1. .0..1..0. .1..0..1. .1..0..0. .1..0..1. .0..0..0. .0..1..1 %e A284450 ..1..0..1. .0..0..1. .0..0..1. .1..1..1. .1..0..1. .0..0..1. .0..1..1 %e A284450 ..1..0..0. .0..1..1. .1..0..0. .1..0..0. .0..0..0. .1..1..1. .0..1..0 %e A284450 ..1..0..0. .0..1..1. .1..0..0. .0..0..0. .1..0..0. .1..0..0. .1..0..0 %Y A284450 Cf. A284455. %K A284450 nonn %O A284450 1,3 %A A284450 _R. H. Hardin_, Mar 27 2017