A208867 Number of n X 3 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or right-upward antidiagonal neighbors.

5, 136, 6520, 324682, 16205218, 808928836, 40380275500, 2015711853262, 100620769519078, 5022810805035976, 250729829501722000, 12515989521112631602, 624776054783641480618, 31187715359825604175756

Offset: 1

Author

R. H. Hardin, Mar 02 2012

Keywords

• nonn

Comments

Column 3 of A208872.

Examples

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

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Crossrefs

Cf. A208872.

Formula

Empirical: a(n) = 55*a(n-1) -261*a(n-2) +369*a(n-3) -162*a(n-4) for n>5.

Empirical g.f.: x*(5 - 139*x + 345*x^2 - 267*x^3 + 54*x^4) / ((1 - x)*(1 - 3*x)*(1 - 51*x + 54*x^2)). - Colin Barker, Jul 07 2018