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 A301779 #4 Mar 26 2018 16:24:42 %S A301779 4,32,240,1808,13616,102544,772272,5816080,43801648,329875856, %T A301779 2484337584,18709866512,140906415920,1061184377488,7991916306096, %U A301779 60188151652624,453284726792752,3413745694159760,25709358766289328,193620494140664336 %N A301779 Number of nX3 0..1 arrays with every element equal to 0, 1, 2 or 3 horizontally or vertically adjacent elements, with upper left element zero. %C A301779 Column 3 of A301784. %H A301779 R. H. Hardin, <a href="/A301779/b301779.txt">Table of n, a(n) for n = 1..210</a> %F A301779 Empirical: a(n) = 7*a(n-1) +4*a(n-2) %e A301779 Some solutions for n=5 %e A301779 ..0..1..0. .0..0..0. .0..0..1. .0..0..1. .0..1..0. .0..1..1. .0..0..1 %e A301779 ..1..1..0. .0..1..0. .1..1..1. .0..0..0. .1..1..1. .1..0..0. .0..0..1 %e A301779 ..0..0..0. .1..0..1. .0..0..1. .1..1..0. .1..0..0. .0..1..1. .0..0..0 %e A301779 ..1..0..1. .1..1..0. .1..1..0. .1..1..1. .0..1..1. .0..1..0. .0..1..0 %e A301779 ..0..0..1. .0..0..0. .1..0..1. .1..0..0. .0..0..1. .1..0..0. .1..0..0 %Y A301779 Cf. A301784. %K A301779 nonn %O A301779 1,1 %A A301779 _R. H. Hardin_, Mar 26 2018