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 A266683 #6 Aug 12 2016 06:53:59 %S A266683 6,101,2520,77830,2643025,96489721,3689693411,146213224799, %T A266683 5947278854261,246989317561499,10427536481704470,446242967428521164, %U A266683 19312763398154267341,843835503392824253913,37171868113841641865335 %N A266683 Number of 4Xn arrays containing n copies of 0..4-1 with no element 1 greater than its northwest or northeast neighbor modulo 4 and the upper left element equal to 0. %C A266683 Row 4 of A266681. %H A266683 R. H. Hardin, <a href="/A266683/b266683.txt">Table of n, a(n) for n = 1..16</a> %e A266683 Some solutions for n=4 %e A266683 ..0..0..2..0....0..1..0..1....0..2..1..3....0..1..1..2....0..3..3..0 %e A266683 ..3..2..3..1....3..3..1..0....1..3..2..3....0..3..0..3....2..2..3..3 %e A266683 ..2..3..1..3....2..3..3..0....3..1..2..1....1..2..3..2....2..1..2..1 %e A266683 ..1..1..2..0....2..1..2..2....0..2..0..0....2..1..0..3....0..1..0..1 %Y A266683 Cf. A266681. %K A266683 nonn %O A266683 1,1 %A A266683 _R. H. Hardin_, Jan 02 2016