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 A207865 #9 Mar 11 2023 20:15:13 %S A207865 2,34,2052,278982,68162042,26419793726,15002771641712, %T A207865 11807624578397830,12361734324171045410,16679505289611340233906, %U A207865 28284296659644702241447604,59055088260515144420128767278,149249218670114328150978145481610 %N A207865 Number of n X 3 nonnegative integer arrays with new values 0 upwards introduced in row major order and no element equal to any horizontal or vertical neighbor (colorings ignoring permutations of colors). %H A207865 Andrew Howroyd, <a href="/A207865/b207865.txt">Table of n, a(n) for n = 1..190</a> (terms 1..20 from R. H. Hardin) %e A207865 Some solutions for n=5 %e A207865 ..0..1..2....0..1..0....0..1..0....0..1..0....0..1..0....0..1..0....0..1..0 %e A207865 ..2..0..1....1..0..1....1..0..1....1..0..1....1..0..2....1..0..1....1..2..1 %e A207865 ..0..1..0....0..1..0....0..1..0....0..1..0....0..1..3....0..1..0....2..0..2 %e A207865 ..1..0..1....1..0..1....1..0..1....1..2..1....1..0..1....2..0..1....0..1..0 %e A207865 ..0..1..0....0..2..0....2..1..0....0..1..0....0..1..2....0..1..0....1..0..1 %Y A207865 Column 3 of A207868. %K A207865 nonn %O A207865 1,1 %A A207865 _R. H. Hardin_, Feb 21 2012