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 A303416 #6 Jan 02 2022 01:11:01 %S A303416 4,32,252,1988,15684,123732,976132,7700788,60752164,479278932, %T A303416 3781071812,29829193588,235325017444,1856498858132,14646075660292, %U A303416 115544122910388,911537305199524,7191194479141332,56731938168469572,447563032495731188 %N A303416 Number of n X 3 0..1 arrays with every element equal to 0, 1, 2, 3, 4 or 5 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A303416 Column 3 of A303421. %H A303416 R. H. Hardin, <a href="/A303416/b303416.txt">Table of n, a(n) for n = 1..210</a> %F A303416 Empirical: a(n) = 7*a(n-1) +6*a(n-2) +8*a(n-3). %e A303416 Some solutions for n=5 %e A303416 ..0..1..0. .0..1..1. .0..0..1. .0..1..1. .0..0..1. .0..1..0. .0..0..0 %e A303416 ..1..0..0. .0..0..0. .1..0..0. .0..0..1. .1..0..0. .0..1..0. .0..1..1 %e A303416 ..0..0..0. .1..0..0. .0..0..0. .0..0..0. .0..1..1. .1..1..1. .1..1..1 %e A303416 ..0..1..1. .0..0..1. .1..1..0. .0..1..0. .0..0..0. .1..1..1. .0..0..0 %e A303416 ..1..1..0. .0..1..1. .1..0..1. .1..0..0. .1..0..0. .1..0..0. .1..0..1 %Y A303416 Cf. A303421. %K A303416 nonn %O A303416 1,1 %A A303416 _R. H. Hardin_, Apr 23 2018