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

1,1

Comments

Column 2 of A205823.

Links

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

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

Example

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

Crossrefs

Cf. A205823.

Sequence in context: A202647 A202640 A074873 * A046393 A268582 A117306

Adjacent sequences: A205814 A205815 A205816 * A205818 A205819 A205820

Keyword

nonn

Author

R. H. Hardin, Feb 01 2012

Status

approved