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 A302064 #6 Jun 09 2023 08:04:41 %S A302064 4,25,148,884,5296,31760,190528,1143104,6858496,41150720,246903808, %T A302064 1481421824,8888528896,53331169280,319987007488,1919922028544, %U A302064 11519532138496,69117192765440,414703156461568,2488218938507264 %N A302064 Number of n X 3 0..1 arrays with every element equal to 0, 1, 2 or 4 horizontally or antidiagonally adjacent elements, with upper left element zero. %C A302064 Column 3 of A302069. %H A302064 R. H. Hardin, <a href="/A302064/b302064.txt">Table of n, a(n) for n = 1..210</a> %F A302064 Empirical: a(n) = 8*a(n-1) - 12*a(n-2) for n>3. %e A302064 Some solutions for n=5 %e A302064 ..0..1..0. .0..1..1. .0..1..1. .0..0..1. .0..0..1. .0..0..1. .0..0..1 %e A302064 ..0..1..1. .0..0..0. .0..0..1. .1..1..0. .1..0..1. .0..0..0. .0..1..0 %e A302064 ..0..0..1. .1..0..0. .1..0..1. .0..1..1. .1..0..0. .1..0..1. .0..0..0 %e A302064 ..1..1..0. .1..0..1. .0..1..0. .0..1..0. .1..1..0. .0..0..1. .0..1..1 %e A302064 ..0..1..1. .0..1..0. .1..0..1. .1..1..1. .1..0..0. .0..1..1. .1..1..0 %Y A302064 Cf. A302069. %K A302064 nonn %O A302064 1,1 %A A302064 _R. H. Hardin_, Mar 31 2018