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 A199129 #7 Jul 22 2025 13:10:52 %S A199129 3,12,19,258,1409,2836,48320,295092,629776,11499816,73045294, %T A199129 159683856,3012721252,19537447260,43276955012,832789320948, %U A199129 5471578311520,12222775051564,238366172778672,1580313985819656,3551105861275344 %N A199129 Number of nX4 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 A199129 Column 4 of A199133 %H A199129 R. H. Hardin, <a href="/A199129/b199129.txt">Table of n, a(n) for n = 1..75</a> %e A199129 Some solutions for n=5 %e A199129 ..0..1..0..2....0..1..0..1....0..1..2..1....0..1..2..1....0..1..2..0 %e A199129 ..1..0..2..1....2..0..2..0....2..0..1..2....2..0..1..2....1..2..0..2 %e A199129 ..2..1..0..2....1..2..1..2....0..2..0..1....1..2..0..1....2..1..2..1 %e A199129 ..1..0..2..1....0..1..2..1....2..0..1..2....2..0..1..0....0..2..1..0 %e A199129 ..0..2..1..0....1..2..0..2....0..2..0..1....0..1..0..2....2..1..0..1 %K A199129 nonn %O A199129 1,1 %A A199129 _R. H. Hardin_ Nov 03 2011