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 A268903 #4 Feb 15 2016 14:57:46 %S A268903 576,34344,1585800,66210264,2611960344,99308573208,3679171151832, %T A268903 133712637011640,4788143315276472,169455769674019992, %U A268903 5940079034652505944,206577531186380751096,7136252899974195705720,245118805391945325271896 %N A268903 Number of nX7 0..2 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two exactly once. %C A268903 Column 7 of A268904. %H A268903 R. H. Hardin, <a href="/A268903/b268903.txt">Table of n, a(n) for n = 1..210</a> %F A268903 Empirical: a(n) = 84*a(n-1) -2466*a(n-2) +31428*a(n-3) -206469*a(n-4) +750384*a(n-5) -1513404*a(n-6) +1574640*a(n-7) -656100*a(n-8) %e A268903 Some solutions for n=2 %e A268903 ..0..1..0..0..0..0..1. .1..0..1..0..0..0..1. .0..0..0..1..2..2..1 %e A268903 ..2..2..1..0..1..2..1. .1..0..0..0..0..2..2. .1..1..2..2..1..2..2 %Y A268903 Cf. A268904. %K A268903 nonn %O A268903 1,1 %A A268903 _R. H. Hardin_, Feb 15 2016