A198710 Number of n X 3 0..3 arrays with values 0..3 introduced in row major order and no element equal to any horizontal or vertical neighbor.

2, 25, 401, 6548, 107042, 1749965, 28609241, 467717288, 7646461682, 125007943505, 2043688517681, 33411178843628, 546221629207922, 8929887496964645, 145989990956749721, 2386712874803449568, 39019101990629849762

Offset: 1

Author

R. H. Hardin, Oct 29 2011

Keywords

• nonn

Comments

Column 3 of A198715.

Examples

			Some solutions with all values from 0 to 3 for n=4:
..0..1..2....0..1..2....0..1..0....0..1..2....0..1..0....0..1..2....0..1..0
..2..0..3....2..3..1....1..0..1....3..2..3....2..0..2....2..3..0....1..2..3
..0..1..0....0..1..2....0..2..3....2..3..0....0..3..1....0..2..1....3..0..1
..3..2..3....3..2..1....3..0..1....1..2..3....2..1..3....1..0..3....0..3..2
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A198715.

Formula

Empirical: a(n) = 19*a(n-1) - 45*a(n-2) + 27*a(n-3).

Empirical g.f.: x*(2 - 13*x + 16*x^2) / ((1 - x)*(1 - 18*x + 27*x^2)). - Colin Barker, Mar 02 2018