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 A269505 #6 Aug 12 2016 06:55:35 %S A269505 1,1,2,1,6,4,1,14,54,8,1,34,420,600,16,1,92,3088,18332,9102,32,1,258, %T A269505 25226,480440,1261420,188472,64,1,722,239994,13522204,135988690, %U A269505 134871120,5118012,128,1,2022,2338286,492613956,14911788936,69071316466 %N A269505 T(n,k)=Number of nXk arrays containing k copies of 0..n-1 avoiding the pattern down-up in every row and column. %C A269505 Table starts %C A269505 ...1.........1...........1...........1...........1.........1...........1 %C A269505 ...2.........6..........14..........34..........92.......258.........722 %C A269505 ...4........54.........420........3088.......25226....239994.....2338286 %C A269505 ...8.......600.......18332......480440....13522204.492613956.18677195738 %C A269505 ..16......9102.....1261420...135988690.14911788936 %C A269505 ..32....188472...134871120.69071316466 %C A269505 ..64...5118012.21338020496 %C A269505 .128.172101936 %C A269505 .256 %H A269505 R. H. Hardin, <a href="/A269505/b269505.txt">Table of n, a(n) for n = 1..49</a> %e A269505 Some solutions for n=3 k=4 %e A269505 ..1..0..0..0. .1..2..0..0. .1..0..0..1. .0..0..1..0. .1..1..2..2 %e A269505 ..2..2..1..0. .1..1..2..2. .0..2..2..2. .2..2..1..1. .2..2..1..0 %e A269505 ..2..2..1..1. .0..0..2..1. .0..2..1..1. .0..2..2..1. .0..0..1..0 %Y A269505 Column 1 is A000079(n-1). %Y A269505 Column 2 is A269477. %K A269505 nonn,tabl %O A269505 1,3 %A A269505 _R. H. Hardin_, Feb 28 2016