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 A300467 #6 Dec 27 2023 21:04:58 %S A300467 4,29,160,925,5363,31106,180397,1046223,6067629,35189573,204083997, %T A300467 1183597158,6864341406,39810152164,230881321531,1339009818730, %U A300467 7765666285883,45037438874738,261197278600938,1514828996788371 %N A300467 Number of n X 3 0..1 arrays with every element equal to 0, 1, 2 or 3 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero. %C A300467 Column 3 of A300472. %H A300467 R. H. Hardin, <a href="/A300467/b300467.txt">Table of n, a(n) for n = 1..210</a> %F A300467 Empirical: a(n) = 6*a(n-1) -a(n-2) -a(n-3) +a(n-4) -4*a(n-5) +a(n-6) -a(n-7). %e A300467 Some solutions for n=5 %e A300467 ..0..0..0. .0..1..1. .0..0..1. .0..1..0. .0..0..0. .0..0..1. .0..1..0 %e A300467 ..1..1..1. .1..0..1. .0..1..1. .1..1..0. .1..1..0. .0..0..1. .0..1..1 %e A300467 ..0..0..0. .0..1..0. .0..0..0. .0..0..1. .1..1..0. .1..1..0. .0..0..1 %e A300467 ..1..1..1. .0..0..1. .0..1..0. .1..0..1. .0..0..1. .0..1..0. .0..0..0 %e A300467 ..1..0..1. .0..1..1. .0..1..1. .0..1..0. .1..0..1. .1..0..1. .1..1..1 %Y A300467 Cf. A300472. %K A300467 nonn %O A300467 1,1 %A A300467 _R. H. Hardin_, Mar 06 2018