A205817 Number of (n+1) X 3 0..2 arrays with the number of clockwise edge increases in every 2 X 2 subblock unequal to the number of counterclockwise edge increases.

66, 216, 714, 2430, 8274, 28242, 96402, 329130, 1123698, 3836538, 13098738, 44721882, 152690034, 521316378, 1779885426, 6076908954, 20747864946, 70837641882, 241854837618, 825744066714, 2819266591602, 9625578232986

Offset: 1

Author

R. H. Hardin, Feb 01 2012

Keywords

• nonn

Comments

Column 2 of A205823.

Examples

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

Links

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

Crossrefs

Cf. A205823.

Formula

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

Empirical g.f.: 6*x*(11 - 8*x - 14*x^2 + 9*x^3) / ((1 - x)*(1 + x)*(1 - 4*x + 2*x^2)). - Colin Barker, Jun 12 2018