A232950 Number of n X 3 0..3 arrays with no element x(i,j) adjacent to value 3-x(i,j) horizontally, diagonally or antidiagonally, and top left element zero.

9, 129, 1881, 27441, 400329, 5840289, 85202361, 1242993681, 18133691049, 264547403649, 3859408908441, 56303849204721, 821401284620169, 11983196174074209, 174819534903392121, 2550393846506436561

Offset: 1

Author

R. H. Hardin, Dec 02 2013

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 3 of A232955.

Formula

Empirical: a(n) = 15*a(n-1) - 6*a(n-2).

Conjectures from Colin Barker, Oct 06 2018: (Start)

G.f.: 3*x*(3 - 2*x) / (1 - 15*x + 6*x^2).

a(n) = (2^(-1-n)*((15-sqrt(201))^n*(-3+sqrt(201)) + (3+sqrt(201))*(15+sqrt(201))^n)) / sqrt(201).

(End)