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 A268909 #4 Feb 15 2016 15:03:39 %S A268909 0,33792,715392,14644152,282550680,5344944120,99308573208, %T A268909 1821165633864,33033242938536,593761996675728,10591066349377632, %U A268909 187684309946743128,3307315733915348808,57997191529735867080,1012715407159459735536 %N A268909 Number of 6Xn 0..2 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two exactly once. %C A268909 Row 6 of A268904. %H A268909 R. H. Hardin, <a href="/A268909/b268909.txt">Table of n, a(n) for n = 1..210</a> %F A268909 Empirical: a(n) = 60*a(n-1) -1466*a(n-2) +19056*a(n-3) -143515*a(n-4) +608478*a(n-5) -957350*a(n-6) -3924114*a(n-7) +27201539*a(n-8) -68079378*a(n-9) +46537423*a(n-10) +212613240*a(n-11) -785654632*a(n-12) +1389943104*a(n-13) -1544105168*a(n-14) +1125401088*a(n-15) -524553472*a(n-16) +142135296*a(n-17) -17040384*a(n-18) for n>26 %e A268909 Some solutions for n=2 %e A268909 ..1..0. .0..0. .2..0. .0..1. .0..1. .1..1. .1..2. .0..1. .0..2. .1..0 %e A268909 ..1..0. .1..2. .1..2. .0..2. .0..0. .2..2. .2..1. .0..2. .2..2. .1..0 %e A268909 ..1..1. .1..0. .1..2. .2..1. .1..0. .1..2. .2..1. .2..2. .1..2. .0..1 %e A268909 ..0..0. .1..0. .1..0. .2..1. .1..2. .2..2. .2..1. .2..2. .2..1. .2..1 %e A268909 ..1..2. .1..2. .1..2. .2..2. .0..1. .2..1. .2..2. .2..1. .0..1. .1..0 %e A268909 ..1..2. .1..1. .1..2. .2..1. .0..1. .0..0. .0..0. .2..2. .2..2. .0..0 %Y A268909 Cf. A268904. %K A268909 nonn %O A268909 1,2 %A A268909 _R. H. Hardin_, Feb 15 2016