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 A268975 #4 Feb 16 2016 13:56:24 %S A268975 243,8448,114048,1504656,18852912,231730344,2799406656,33382885464, %T A268975 393837138576,4605236160408,53449814746368,616434849399384, %U A268975 7070720929863408,80721453100802904,917737124914636128 %N A268975 Number of 5Xn 0..2 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two not more than once. %C A268975 Row 5 of A268971. %H A268975 R. H. Hardin, <a href="/A268975/b268975.txt">Table of n, a(n) for n = 1..210</a> %F A268975 Empirical: a(n) = 32*a(n-1) -384*a(n-2) +2200*a(n-3) -6494*a(n-4) +9016*a(n-5) -816*a(n-6) -14888*a(n-7) +18879*a(n-8) -5464*a(n-9) -7472*a(n-10) +8336*a(n-11) -3648*a(n-12) +768*a(n-13) -64*a(n-14) for n>18 %e A268975 Some solutions for n=3 %e A268975 ..1..0..1. .0..2..2. .2..1..2. .0..0..0. .2..1..2. .0..1..2. .0..1..0 %e A268975 ..1..2..1. .1..2..1. .0..1..0. .1..0..0. .0..1..0. .0..1..0. .0..0..1 %e A268975 ..2..2..2. .1..0..0. .0..1..2. .0..0..0. .2..1..2. .0..0..1. .2..2..2 %e A268975 ..1..2..2. .0..0..0. .0..1..2. .1..0..1. .2..2..1. .0..1..0. .1..2..1 %e A268975 ..1..1..2. .0..1..0. .2..1..1. .1..0..2. .1..0..0. .0..0..0. .1..2..2 %Y A268975 Cf. A268971. %K A268975 nonn %O A268975 1,1 %A A268975 _R. H. Hardin_, Feb 16 2016