A207454 Number of 3 X n 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 0 1 and 1 0 1 vertically.

6, 36, 90, 330, 1008, 3354, 10710, 34884, 112530, 364722, 1179360, 3817938, 12352782, 39978180, 129366090, 418647162, 1354755024, 4384104618, 14187219750, 45910873476, 148570600866, 480784736226, 1555851810240, 5034842671650

Offset: 1

Author

R. H. Hardin, Feb 17 2012

Keywords

• nonn

Comments

Row 3 of A207453.

Examples

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

Links

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

Crossrefs

Cf. A207453.

Formula

Empirical: a(n) = a(n-1) + 7*a(n-2) + 2*a(n-3) - 4*a(n-4).

Empirical g.f.: 6*x*(1 + 5*x + 2*x^2 - 4*x^3) / ((1 + x - x^2)*(1 - 2*x - 4*x^2)). - Colin Barker, Mar 05 2018