A205829 Number of (n+1) X 2 0..2 arrays with the number of clockwise edge increases in every 2 X 2 subblock equal to two.

30, 111, 423, 1611, 6132, 23340, 88839, 338148, 1287093, 4899063, 18647307, 70977258, 270160788, 1028313201, 3914069274, 14898124683, 56706742659, 215842915227, 821563042932, 3127115999160, 11902743868935, 45305422519512

Offset

1,1

Comments

Column 1 of A205836.

Links

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

Formula

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

Empirical g.f.: 3*x*(10 - 3*x + 3*x^2) / (1 - 4*x + x^2 - x^3). - Colin Barker, Jun 12 2018

Example

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

Crossrefs

Cf. A205836.

Sequence in context: A043466 A044281 A044662 * A304836 A010018 A256649

Adjacent sequences: A205826 A205827 A205828 * A205830 A205831 A205832

Keyword

nonn

Author

R. H. Hardin, Feb 01 2012

Status

approved