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).

2, 7, 270, 27093, 5252041, 1688298227, 819147302097, 562766251199622, 522687453434959180, 633631710314384052082, 975235769907492737264795, 1863659976446678796423595540, 4341202639797991970260869847084, 12137362722177750192276998364963783

Offset: 1

Author

R. H. Hardin, Feb 22 2012

Keywords

• nonn

Examples

			Some solutions for n=4
..0..1..0....0..1..0....0..1..0....0..1..2....0..1..0....0..1..2....0..1..0
..2..3..2....2..3..2....2..3..2....2..3..0....2..3..2....2..3..4....2..3..2
..4..0..4....0..1..0....4..1..0....4..5..4....0..1..0....5..6..0....0..1..0
..1..2..1....2..3..2....5..2..3....0..1..2....2..3..4....2..3..1....3..2..3
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..100

Crossrefs

Column 3 of A208021.

Extensions

Terms a(14) and beyond from Andrew Howroyd, Jun 25 2017