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 A269048 #7 Jan 18 2019 16:24:54 %S A269048 60,360,3078,24192,183072,1350672,9779808,69793968,492374976, %T A269048 3441051984,23861339424,164375084016,1125975740544,7675458754704, %U A269048 52099028628960,352309891913520,2374503933353280,15956129491021776,106934858162261664 %N A269048 Number of n X 4 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two not more than once. %H A269048 R. H. Hardin, <a href="/A269048/b269048.txt">Table of n, a(n) for n = 1..210</a> %F A269048 Empirical: a(n) = 14*a(n-1) - 57*a(n-2) + 56*a(n-3) - 16*a(n-4) for n>5. %F A269048 Empirical g.f.: 6*x*(10 - 80*x + 243*x^2 - 290*x^3 + 105*x^4) / (1 - 7*x + 4*x^2)^2. - _Colin Barker_, Jan 18 2019 %e A269048 Some solutions for n=4: %e A269048 ..0..1..2..0. .2..1..2..1. .1..2..1..2. .0..0..0..1. .2..1..1..2 %e A269048 ..0..1..0..1. .2..1..0..1. .1..2..1..2. .0..0..0..0. .2..2..2..2 %e A269048 ..0..0..0..0. .2..1..2..0. .2..2..2..2. .0..0..0..1. .2..2..2..1 %e A269048 ..0..1..0..0. .2..1..0..1. .1..1..2..1. .1..0..0..0. .2..1..2..1 %Y A269048 Column 4 of A269052. %K A269048 nonn %O A269048 1,1 %A A269048 _R. H. Hardin_, Feb 18 2016