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 A199131 #7 Jul 22 2025 13:11:06 %S A199131 5,30,264,2836,33970,438502,5926852,82908094,1187201812,17307138986, %T A199131 255687902462,3817658150424,57485010058768,871667490461400, %U A199131 13295046323445896,203799010704532580,3137556683409570358 %N A199131 Number of nX6 0..2 arrays with values 0..2 introduced in row major order, the number of instances of each value within one of each other, and no element equal to any horizontal or vertical neighbor. %C A199131 Column 6 of A199133 %H A199131 R. H. Hardin, <a href="/A199131/b199131.txt">Table of n, a(n) for n = 1..34</a> %e A199131 Some solutions for n=5 %e A199131 ..0..1..0..1..2..1....0..1..0..1..2..1....0..1..0..2..1..2....0..1..2..1..0..2 %e A199131 ..2..0..2..0..1..2....2..0..1..2..1..2....2..0..1..0..2..0....2..0..1..2..1..0 %e A199131 ..0..2..1..2..0..1....1..2..0..1..0..1....1..2..0..2..0..1....0..1..2..1..2..1 %e A199131 ..2..0..2..0..1..2....2..0..2..0..2..0....0..1..2..0..1..2....1..0..1..2..0..2 %e A199131 ..0..1..0..1..2..1....1..2..0..1..0..2....1..2..1..2..0..1....0..2..0..1..2..0 %K A199131 nonn %O A199131 1,1 %A A199131 _R. H. Hardin_ Nov 03 2011