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 A269137 #10 Jan 19 2019 08:44:39 %S A269137 16,148,1164,8532,59916,408596,2727564,17914580,116170764,745617300, %T A269137 4745165964,29984668756,188330955276,1176750424852,7319499656844, %U A269137 45347466532308,279961285570572,1722988944076436,10574188575966348 %N A269137 Number of n X 2 0..3 arrays with some element plus some horizontally, antidiagonally or vertically adjacent neighbor totalling three no more than once. %H A269137 R. H. Hardin, <a href="/A269137/b269137.txt">Table of n, a(n) for n = 1..210</a> %F A269137 Empirical: a(n) = 12*a(n-1) - 38*a(n-2) + 12*a(n-3) - a(n-4) for n>5. %F A269137 Empirical g.f.: 4*x*(4 - 11*x - x^2 - x^3 + x^4) / (1 - 6*x + x^2)^2. - _Colin Barker_, Jan 19 2019 %e A269137 Some solutions for n=4: %e A269137 ..2..0. .3..3. .1..0. .2..2. .3..0. .2..1. .0..0. .0..1. .3..3. .0..1 %e A269137 ..2..2. .1..1. .1..1. .2..3. .1..0. .0..1. .0..1. .0..0. .1..1. .0..3 %e A269137 ..3..1. .1..3. .3..1. .0..1. .0..1. .1..1. .1..1. .1..2. .1..1. .1..1 %e A269137 ..1..1. .3..3. .0..0. .0..1. .0..0. .3..1. .0..2. .0..2. .3..0. .1..0 %Y A269137 Column 2 of A269143. %K A269137 nonn %O A269137 1,1 %A A269137 _R. H. Hardin_, Feb 20 2016