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 A268907 #4 Feb 15 2016 15:02:12 %S A268907 0,1344,12960,118584,1004184,8250912,66210264,522241560,4063962024, %T A268907 31282792704,238663638432,1807307152056,13599932970888, %U A268907 101786388133320,758232651966984,5625079743143376,41579318178922608,306353541215271960 %N A268907 Number of 4Xn 0..2 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two exactly once. %C A268907 Row 4 of A268904. %H A268907 R. H. Hardin, <a href="/A268907/b268907.txt">Table of n, a(n) for n = 1..210</a> %F A268907 Empirical: a(n) = 18*a(n-1) -111*a(n-2) +282*a(n-3) -333*a(n-4) +180*a(n-5) -36*a(n-6) for n>12 %e A268907 Some solutions for n=4 %e A268907 ..0..1..0..0. .0..0..0..1. .2..1..0..1. .1..0..0..0. .1..1..2..2 %e A268907 ..0..1..0..0. .0..0..0..1. .2..1..2..2. .1..0..1..0. .2..2..1..0 %e A268907 ..2..1..2..1. .0..0..0..1. .1..2..2..2. .0..0..1..2. .1..0..1..0 %e A268907 ..0..1..2..1. .1..0..2..2. .2..2..1..2. .0..0..2..2. .0..0..0..1 %Y A268907 Cf. A268904. %K A268907 nonn %O A268907 1,2 %A A268907 _R. H. Hardin_, Feb 15 2016