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 A269508 #5 Aug 12 2016 06:54:17 %S A269508 8,600,18332,480440,13522204,492613956,18677195738,753228526960, %T A269508 29963202454514,1236592684106800 %N A269508 Number of 4Xn arrays containing n copies of 0..4-1 avoiding the pattern down-up in every row and column. %C A269508 Row 4 of A269505. %e A269508 Some solutions for n=3 %e A269508 ..3..0..0. .2..1..0. .2..2..0. .0..1..0. .0..2..0. .3..2..1. .0..2..1 %e A269508 ..1..2..0. .2..2..0. .3..3..1. .1..3..0. .3..2..2. .0..3..2. .2..3..3 %e A269508 ..1..2..1. .1..3..0. .0..3..2. .2..3..1. .1..3..1. .0..1..3. .2..3..1 %e A269508 ..3..3..2. .1..3..3. .0..1..1. .3..2..2. .1..3..0. .2..1..0. .0..0..1 %Y A269508 Cf. A269505. %K A269508 nonn %O A269508 1,1 %A A269508 _R. H. Hardin_, Feb 28 2016