A208858 Number of n X 2 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 left-upward diagonal neighbors.

2, 11, 127, 1691, 23047, 315203, 4313071, 59022155, 807696535, 11053048211, 151257183487, 2069902880411, 28325913895207, 387630456564323, 5304590398318351, 72591507756551915, 993389989178417335

Offset: 1

Author

R. H. Hardin, Mar 02 2012

Keywords

• nonn

Comments

Column 2 of A208864.

Examples

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

Links

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

Crossrefs

Cf. A208864.

Formula

Empirical: a(n) = 17*a(n-1) - 48*a(n-2) + 36*a(n-3) for n>4.

Empirical g.f.: x*(2 - 23*x + 36*x^2 - 12*x^3) / ((1 - 2*x)*(1 - 15*x + 18*x^2)). - Colin Barker, Jul 07 2018