A183476 Number of n X 2 0..2 arrays with every element equal to either the sum mod 3 of its vertical neighbors or the sum mod 3 of its horizontal neighbors.

3, 15, 39, 135, 495, 1647, 5751, 20223, 70119, 244863, 855927, 2985903, 10426887, 36416223, 127148535, 444006927, 1550518119, 5414352255, 18907098327, 66024403695, 230558764743, 805118884191, 2811503074743, 9817858453455

Offset: 1

Author

R. H. Hardin, Jan 05 2011

Keywords

• nonn

Comments

Column 2 of A183483.

Examples

			Some solutions for 4 X 2.
..2..2....2..2....1..1....0..0....2..2....0..0....0..0....2..2....0..0....1..1
..0..0....2..2....0..2....0..0....1..1....1..1....2..0....0..0....2..2....1..1
..1..1....0..0....2..1....1..1....0..0....1..1....2..0....2..2....1..1....2..2
..0..0....1..1....2..2....0..0....2..2....1..1....0..0....2..2....1..1....0..0
		

Links

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

Crossrefs

Cf. A183483.

Formula

Empirical: a(n) = 3*a(n-1) + 12*a(n-3) - 18*a(n-4) - 36*a(n-6).

Empirical g.f.: 3*x*(1 + 2*x - 2*x^2 - 6*x^3 - 12*x^4 - 12*x^5) / ((1 - 6*x^3)*(1 - 3*x - 6*x^3)). - Colin Barker, Mar 29 2018