A234825 Number of (n+1) X (1+1) 0..2 arrays with each 2 X 2 subblock having the number of clockwise edge increases less than or equal to the number of counterclockwise edge increases.

69, 516, 3843, 28602, 212850, 1583955, 11787201, 87715899, 652748544, 4857507711, 36147734568, 268997764212, 2001779586225, 14896486309185, 110854015040601, 824933638413864, 6138844024165119, 45682954601641506, 339955264040033718

Offset

1,1

Links

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

Formula

Empirical: a(n) = 9*a(n-1) - 12*a(n-2) + 3*a(n-3).

Empirical g.f.: 3*x*(23 - 35*x + 9*x^2) / (1 - 9*x + 12*x^2 - 3*x^3). - Colin Barker, Oct 16 2018

Example

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

Crossrefs

Column 1 of A234832.

Sequence in context: A253342 A253335 A234832 * A251010 A251003 A211692

Adjacent sequences: A234822 A234823 A234824 * A234826 A234827 A234828

Keyword

nonn

Author

R. H. Hardin, Dec 31 2013

Status

approved