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 A267726 #6 Aug 12 2016 06:54:16 %S A267726 0,2,2,30,58,588,2388,17456,102874,731154,5027962,36610288,266876496, %T A267726 1982397806,14796809106,111298650288,840466993090,6372988144620, %U A267726 48466708273020,369602842446350,2824995007935614,21637397279211678 %N A267726 Number of 3Xn arrays containing n copies of 0..3-1 with every element equal to at least one horizontal neighbor and the top left element equal to 0. %C A267726 Row 3 of A267724. %H A267726 R. H. Hardin, <a href="/A267726/b267726.txt">Table of n, a(n) for n = 1..38</a> %e A267726 Some solutions for n=4 %e A267726 ..0..0..0..0....0..0..2..2....0..0..1..1....0..0..0..0....0..0..2..2 %e A267726 ..2..2..1..1....1..1..0..0....1..1..2..2....2..2..1..1....1..1..1..1 %e A267726 ..1..1..2..2....1..1..2..2....2..2..0..0....2..2..1..1....0..0..2..2 %Y A267726 Cf. A267724. %K A267726 nonn %O A267726 1,2 %A A267726 _R. H. Hardin_, Jan 20 2016