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 A268160 #6 Aug 12 2016 06:54:17 %S A268160 0,0,8,14,52,1516,7582,46338,501270,3535396,25480614,220369120, %T A268160 1716544860,13279246254,108919001860,873463942418,6971258302462, %U A268160 56716000746978,460015101808320,3726764125840338,30399952923410062 %N A268160 Number of 3Xn arrays containing n copies of 0..3-1 with every element equal to at least one vertical or antidiagonal neighbor and the top left element equal to 0. %C A268160 Row 3 of A268159. %H A268160 R. H. Hardin, <a href="/A268160/b268160.txt">Table of n, a(n) for n = 1..68</a> %e A268160 Some solutions for n=4 %e A268160 ..0..1..1..2....0..0..2..2....0..1..1..2....0..0..1..2....0..1..2..2 %e A268160 ..0..1..2..0....0..1..2..1....0..1..0..2....0..1..2..1....0..1..2..0 %e A268160 ..1..2..2..0....0..1..2..1....1..0..2..2....0..2..2..1....1..1..2..0 %Y A268160 Cf. A268159. %K A268160 nonn %O A268160 1,3 %A A268160 _R. H. Hardin_, Jan 27 2016