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 A304265 #4 May 09 2018 10:11:31 %S A304265 3,3,6,10,19,37,67,124,235,436,808,1513,2821,5245,9784,18247,33982, %T A304265 63334,118075,220021,410023,764248,1424311,2654380,4947124,9220057, %U A304265 17183197,32024569,59684740,111234331,207308038,386362258,720065251,1341989365 %N A304265 Number of nX3 0..1 arrays with every element unequal to 0, 1, 5 or 8 king-move adjacent elements, with upper left element zero. %C A304265 Column 3 of A304270. %H A304265 R. H. Hardin, <a href="/A304265/b304265.txt">Table of n, a(n) for n = 1..210</a> %F A304265 Empirical: a(n) = a(n-1) +3*a(n-3) for n>4 %e A304265 Some solutions for n=5 %e A304265 ..0..0..0. .0..1..0. .0..0..0. .0..0..0. .0..0..0. .0..1..0. .0..0..0 %e A304265 ..1..0..0. .0..0..0. .0..0..0. .0..0..1. .0..0..0. .0..0..0. .0..0..0 %e A304265 ..0..0..0. .0..0..0. .0..0..1. .0..0..0. .0..0..0. .0..0..0. .0..0..0 %e A304265 ..0..0..0. .1..0..0. .0..0..0. .0..0..0. .0..0..0. .0..0..0. .0..0..1 %e A304265 ..0..0..0. .0..0..0. .0..0..0. .0..1..0. .0..0..0. .0..0..0. .0..0..0 %Y A304265 Cf. A304270. %K A304265 nonn %O A304265 1,1 %A A304265 _R. H. Hardin_, May 09 2018