A233021 Number of n X 3 0..3 arrays with no element x(i,j) adjacent to value 3-x(i,j) horizontally, vertically, diagonally or antidiagonally, and top left element zero.

9, 81, 849, 8835, 92067, 959385, 9997413, 104179551, 1085618895, 11312857317, 117887355777, 1228463178219, 12801387988827, 133398816787089, 1390102724464989, 14485777543658775, 150951255149241255

Offset: 1

Author

R. H. Hardin, Dec 03 2013

Keywords

• nonn

Examples

			Some solutions for n=5:
..0..1..0....0..0..1....0..0..0....0..1..0....0..1..3....0..0..0....0..1..0
..0..1..1....1..1..1....2..2..2....1..1..0....0..1..1....0..2..0....0..1..1
..0..1..0....3..3..3....3..2..0....1..0..0....1..1..1....2..0..2....1..1..1
..1..1..1....1..1..1....3..2..2....0..0..0....1..3..3....2..0..2....1..3..3
..1..0..0....3..3..1....2..2..2....0..0..2....1..1..1....2..2..2....3..3..2
		

Links

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

Crossrefs

Column 3 of A233026.

Formula

Empirical: a(n) = 11*a(n-1) - 5*a(n-2) - 11*a(n-3) + 2*a(n-4).

Empirical g.f.: 3*x*(3 - 6*x + x^2) / (1 - 11*x + 5*x^2 + 11*x^3 - 2*x^4). - Colin Barker, Oct 07 2018