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 A302146 #4 Apr 02 2018 14:24:48 %S A302146 1,2,4,10,28,84,260,816,2576,8152,25824,81840,259408,822304,2606720, %T A302146 8263456,26195776,83042752,263252544,834533120,2645541888,8386596224, %U A302146 26586234880,84280663296,267176990976,846974167552,2684981361664 %N A302146 Number of nX3 0..1 arrays with every element equal to 0, 2, 3 or 4 horizontally or antidiagonally adjacent elements, with upper left element zero. %C A302146 Column 3 of A302150. %H A302146 R. H. Hardin, <a href="/A302146/b302146.txt">Table of n, a(n) for n = 1..210</a> %F A302146 Empirical: a(n) = 4*a(n-1) -2*a(n-2) -2*a(n-3) %e A302146 Some solutions for n=5 %e A302146 ..0..1..1. .0..1..1. .0..1..0. .0..1..0. .0..1..1. .0..1..1. .0..1..0 %e A302146 ..1..1..0. .1..1..0. .0..1..0. .0..1..0. .1..1..0. .1..1..0. .0..1..1 %e A302146 ..0..1..1. .1..1..1. .0..1..0. .0..1..1. .1..1..0. .0..1..0. .1..1..1 %e A302146 ..1..1..0. .1..1..1. .0..1..1. .1..1..0. .1..1..1. .0..1..0. .0..1..1 %e A302146 ..0..1..0. .1..1..0. .1..1..0. .0..1..0. .1..1..0. .0..1..0. .1..1..0 %Y A302146 Cf. A302150. %K A302146 nonn %O A302146 1,2 %A A302146 _R. H. Hardin_, Apr 02 2018