A267899 Number of nX3 arrays containing 3 copies of 0..n-1 with every element equal to at least one horizontal or vertical neighbor and the top left element equal to 0.

1, 3, 20, 138, 1488, 20400, 317520, 5911920, 126080640, 2999566080, 79604985600

Offset: 1

Author

R. H. Hardin, Jan 22 2016

Keywords

• nonn

Comments

Column 3 of A267901.

Examples

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

Crossrefs

Cf. A267901.