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 A303309 #4 Apr 21 2018 12:44:59 %S A303309 3,3,12,11,19,34,53,83,136,223,359,578,937,1519,2456,3971,6427,10402, %T A303309 16829,27227,44056,71287,115343,186626,301969,488599,790568,1279163, %U A303309 2069731,3348898,5418629,8767523,14186152,22953679,37139831,60093506 %N A303309 Number of nX3 0..1 arrays with every element equal to 0, 1, 4, 5 or 6 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A303309 Column 3 of A303314. %H A303309 R. H. Hardin, <a href="/A303309/b303309.txt">Table of n, a(n) for n = 1..210</a> %F A303309 Empirical: a(n) = a(n-1) +a(n-3) +a(n-4) for n>7 %e A303309 Some solutions for n=5 %e A303309 ..0..1..0. .0..1..0. .0..1..0. .0..0..1. .0..1..1. .0..0..0. .0..0..0 %e A303309 ..0..1..0. .0..1..0. .0..1..0. .1..1..1. .0..0..0. .0..1..0. .0..1..0 %e A303309 ..0..1..0. .0..0..0. .0..1..0. .1..0..1. .0..1..0. .0..1..0. .0..1..0 %e A303309 ..0..1..0. .1..1..1. .0..0..0. .1..0..1. .0..1..0. .0..0..0. .0..1..0 %e A303309 ..0..0..0. .1..0..1. .0..1..1. .1..0..1. .0..0..0. .1..1..0. .0..1..0 %Y A303309 Cf. A303314. %K A303309 nonn %O A303309 1,1 %A A303309 _R. H. Hardin_, Apr 21 2018