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 A269036 #8 Jan 18 2019 09:57:53 %S A269036 0,24,48,216,672,2208,6912,21408,65280,196992,589056,1748352,5156352, %T A269036 15124992,44156928,128383488,371908608,1073879040,3091820544, %U A269036 8878479360,25435250688,72710922240,207448571904,590798364672,1679765078016 %N A269036 Number of 2 X n 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two exactly once. %H A269036 R. H. Hardin, <a href="/A269036/b269036.txt">Table of n, a(n) for n = 1..210</a> %F A269036 Empirical: a(n) = 4*a(n-1) - 8*a(n-3) - 4*a(n-4). %F A269036 Empirical g.f.: 24*x^2*(1 - x)^2 / (1 - 2*x - 2*x^2)^2. - _Colin Barker_, Jan 18 2019 %e A269036 Some solutions for n=4: %e A269036 ..2..1..0..0. .2..2..2..1. .0..2..2..2. .2..2..1..2. .0..1..0..1 %e A269036 ..2..1..2..1. .2..2..1..2. .2..1..2..1. .1..2..2..1. .2..0..0..1 %Y A269036 Row 2 of A269035. %K A269036 nonn %O A269036 1,2 %A A269036 _R. H. Hardin_, Feb 18 2016