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 A302872 #4 Apr 15 2018 10:30:55 %S A302872 3,11,17,37,82,209,536,1549,4513,13980,44424,142457,463592,1518144, %T A302872 4985864,16423493,54170895,178797985,590488247,1950654770,6444889749, %U A302872 21296082916,70373480203,232558689443,768538881502,2539828012418 %N A302872 Number of nX3 0..1 arrays with every element equal to 0, 1, 3, 4 or 5 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A302872 Column 3 of A302877. %H A302872 R. H. Hardin, <a href="/A302872/b302872.txt">Table of n, a(n) for n = 1..210</a> %F A302872 Empirical: a(n) = 3*a(n-1) +9*a(n-3) -15*a(n-4) -5*a(n-5) -22*a(n-6) -7*a(n-7) +9*a(n-8) -32*a(n-9) -10*a(n-10) -16*a(n-11) -40*a(n-12) -16*a(n-13) for n>16 %e A302872 Some solutions for n=5 %e A302872 ..0..0..1. .0..0..1. .0..0..1. .0..0..1. .0..1..0. .0..0..1. .0..0..0 %e A302872 ..0..1..0. .1..1..1. .0..1..0. .1..1..1. .0..1..0. .1..1..1. .0..1..0 %e A302872 ..0..1..0. .1..0..1. .0..1..0. .1..0..1. .0..1..0. .1..0..1. .0..1..0 %e A302872 ..0..1..0. .1..0..0. .1..1..0. .1..0..1. .0..0..0. .1..0..1. .0..1..0 %e A302872 ..0..0..0. .1..0..1. .0..1..0. .0..1..1. .0..1..1. .1..1..0. .0..1..0 %Y A302872 Cf. A302877. %K A302872 nonn %O A302872 1,1 %A A302872 _R. H. Hardin_, Apr 15 2018