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 A266310 #6 Aug 12 2016 06:53:59 %S A266310 2,7,39,265,1802,12239,84614,597601,4289844,31138558,227912351, %T A266310 1679866698,12457873439,92883320659,695746287346,5232714491851, %U A266310 39496475643074,299071199295812,2271081847307045,17290623003826450 %N A266310 Number of 3Xn arrays containing n copies of 0..3-1 with no element 1 greater than its west neighbor modulo 3 and the upper left element equal to 0. %C A266310 Row 3 of A266309. %H A266310 R. H. Hardin, <a href="/A266310/b266310.txt">Table of n, a(n) for n = 1..83</a> %e A266310 Some solutions for n=4 %e A266310 ..0..0..0..0....0..2..2..1....0..2..1..1....0..2..1..1....0..2..1..0 %e A266310 ..2..1..1..1....1..0..0..2....2..1..0..2....1..0..0..2....0..2..2..2 %e A266310 ..2..2..2..1....1..0..2..1....0..0..2..1....0..2..2..1....1..1..1..0 %Y A266310 Cf. A266309. %K A266310 nonn %O A266310 1,1 %A A266310 _R. H. Hardin_, Dec 26 2015