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 A269181 #4 Feb 20 2016 09:11:10 %S A269181 24,384,5888,80112,1031344,12791896,154606864,1833130768,21416076480, %T A269181 247279304248,2828051682752,32088228414160,361662427633424, %U A269181 4053056289550296,45198059875209904,501865175240768976 %N A269181 Number of nX3 0..3 arrays with some element plus some horizontally, diagonally, antidiagonally or vertically adjacent neighbor totalling three exactly once. %C A269181 Column 3 of A269186. %H A269181 R. H. Hardin, <a href="/A269181/b269181.txt">Table of n, a(n) for n = 1..210</a> %F A269181 Empirical: a(n) = 22*a(n-1) -131*a(n-2) +88*a(n-3) +221*a(n-4) -154*a(n-5) -101*a(n-6) +44*a(n-7) -4*a(n-8) for n>9 %e A269181 Some solutions for n=4 %e A269181 ..1..2..0. .0..0..0. .3..1..2. .1..1..0. .1..0..1. .3..0..1. .3..1..2 %e A269181 ..0..0..2. .2..0..2. .3..3..3. .3..3..1. .0..1..0. .1..1..0. .1..3..3 %e A269181 ..2..0..0. .2..2..2. .1..1..1. .2..3..1. .1..0..2. .1..1..1. .3..3..2 %e A269181 ..2..2..2. .3..0..2. .1..1..0. .3..3..1. .1..0..0. .1..0..0. .2..2..3 %Y A269181 Cf. A269186. %K A269181 nonn %O A269181 1,1 %A A269181 _R. H. Hardin_, Feb 20 2016