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 A266457 #6 Aug 12 2016 06:53:59 %S A266457 2,101,6152,442285,34667512,2875874396,248188720768,22053860939581, %T A266457 2004232543930760,185418855352374916,17404087748977051168, %U A266457 1653341486254703216284,158659220471195369806688 %N A266457 Number of 4Xn arrays containing n copies of 0..4-1 with no element 1 greater than its north neighbor modulo 4 and the upper left element equal to 0. %C A266457 Row 4 of A266455. %H A266457 R. H. Hardin, <a href="/A266457/b266457.txt">Table of n, a(n) for n = 1..39</a> %e A266457 Some solutions for n=3 %e A266457 ..0..2..3....0..3..0....0..1..2....0..0..1....0..2..3....0..1..2....0..2..1 %e A266457 ..2..1..1....2..1..3....3..3..2....0..2..3....0..2..2....3..3..0....3..1..0 %e A266457 ..0..3..0....1..0..2....2..3..0....3..1..2....0..1..1....3..2..2....3..3..0 %e A266457 ..2..1..3....1..3..2....1..1..0....3..1..2....3..3..1....1..0..1....1..2..2 %Y A266457 Cf. A266455. %K A266457 nonn %O A266457 1,1 %A A266457 _R. H. Hardin_, Dec 29 2015