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 A269038 #4 Feb 18 2016 09:02:07 %S A269038 0,504,2136,18384,115656,785124,4998648,31834476,198736752,1231177296, %T A269038 7552688064,46020487500,278641166280,1678349335044,10062618187272, %U A269038 60089435895360,357550261665528,2120806295463156,12543856834626072 %N A269038 Number of 4Xn 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two exactly once. %C A269038 Row 4 of A269035. %H A269038 R. H. Hardin, <a href="/A269038/b269038.txt">Table of n, a(n) for n = 1..210</a> %F A269038 Empirical: a(n) = 6*a(n-1) +23*a(n-2) -102*a(n-3) -288*a(n-4) +250*a(n-5) +787*a(n-6) -238*a(n-7) -741*a(n-8) +124*a(n-9) +196*a(n-10) -16*a(n-11) -16*a(n-12) for n>14 %e A269038 Some solutions for n=4 %e A269038 ..0..1..0..1. .2..2..2..1. .2..2..2..2. .1..0..0..2. .2..2..1..2 %e A269038 ..2..1..2..1. .2..2..2..2. .1..2..2..1. .1..0..1..0. .2..2..2..2 %e A269038 ..0..1..0..1. .2..1..2..1. .1..2..1..2. .0..0..1..0. .2..2..2..2 %e A269038 ..0..0..2..1. .0..2..2..1. .1..2..1..2. .1..0..1..0. .2..2..1..1 %Y A269038 Cf. A269035. %K A269038 nonn %O A269038 1,2 %A A269038 _R. H. Hardin_, Feb 18 2016