A232289 Number of nX2 0..2 arrays with every 0 next to a 1 and every 1 next to a 2 horizontally or antidiagonally.

3, 15, 73, 355, 1727, 8401, 40867, 198799, 967065, 4704323, 22884351, 111321761, 541528771, 2634286479, 12814582761, 62337005731, 303240640447, 1475125167473, 7175800237411, 34906942259983, 169806095157049, 826027949905539

Offset: 1

Author

R. H. Hardin, Nov 22 2013

Keywords

• nonn

Comments

Column 2 of A232295

Examples

			Some solutions for n=7
..2..2....2..1....2..2....2..2....2..2....2..2....1..2....1..2....1..2....1..2
..2..0....0..2....2..0....2..1....0..1....2..1....0..1....1..0....2..1....2..0
..1..2....2..0....1..2....1..2....2..1....2..1....2..1....2..2....1..2....1..2
..2..2....1..2....2..0....2..2....0..2....2..2....0..2....2..1....2..1....1..2
..1..2....2..1....1..2....2..2....0..1....2..1....1..0....0..0....1..2....1..1
..2..0....0..1....1..2....1..2....2..1....2..1....0..1....1..2....2..2....2..1
..1..2....2..2....2..1....1..2....2..2....0..2....2..2....2..2....2..1....2..2
		

Links

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

Formula

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

Empirical: G.f.: -x*(3+3*x+x^2) / ( -1+4*x+4*x^2+x^3 ). - R. J. Mathar, Nov 27 2013