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 A269648 #5 Aug 12 2016 06:54:17 %S A269648 24,1880,68876,2316638,94747953,4581555620,234861499280, %T A269648 12266888439720,650084333233220 %N A269648 Number of 4Xn arrays containing n copies of 0..4-1 avoiding the pattern down-up in every row and equal-up in every column. %C A269648 Row 4 of A269646. %e A269648 Some solutions for n=3 %e A269648 ..0..1..1. .3..2..1. .3..3..2. .0..1..2. .0..1..2. .2..2..0. .3..2..1 %e A269648 ..2..2..3. .0..0..0. .2..2..1. .2..3..3. .3..0..0. .2..3..3. .0..1..3 %e A269648 ..0..0..3. .3..3..2. .3..0..0. .1..0..0. .2..1..1. .1..1..1. .3..2..2 %e A269648 ..1..2..3. .2..1..1. .1..1..0. .1..2..3. .2..3..3. .0..0..3. .1..0..0 %Y A269648 Cf. A269646. %K A269648 nonn %O A269648 1,1 %A A269648 _R. H. Hardin_, Mar 02 2016