cp's OEIS Frontend

A208018 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, vertical, diagonal or antidiagonal neighbor (colorings ignoring permutations of colors).

%I A208018 #10 Jun 25 2017 17:13:12
%S A208018 2,7,270,27093,5252041,1688298227,819147302097,562766251199622,
%T A208018 522687453434959180,633631710314384052082,975235769907492737264795,
%U A208018 1863659976446678796423595540,4341202639797991970260869847084,12137362722177750192276998364963783
%N A208018 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, vertical, diagonal or antidiagonal neighbor (colorings ignoring permutations of colors).
%H A208018 Andrew Howroyd, <a href="/A208018/b208018.txt">Table of n, a(n) for n = 1..100</a>
%e A208018 Some solutions for n=4
%e A208018 ..0..1..0....0..1..0....0..1..0....0..1..2....0..1..0....0..1..2....0..1..0
%e A208018 ..2..3..2....2..3..2....2..3..2....2..3..0....2..3..2....2..3..4....2..3..2
%e A208018 ..4..0..4....0..1..0....4..1..0....4..5..4....0..1..0....5..6..0....0..1..0
%e A208018 ..1..2..1....2..3..2....5..2..3....0..1..2....2..3..4....2..3..1....3..2..3
%Y A208018 Column 3 of A208021.
%K A208018 nonn
%O A208018 1,1
%A A208018 _R. H. Hardin_, Feb 22 2012
%E A208018 Terms a(14) and beyond from _Andrew Howroyd_, Jun 25 2017