A234780 Number of (n+1) X (2+1) 0..3 arrays with no adjacent elements equal and with each 2 X 2 subblock having the number of clockwise edge increases equal to the number of counterclockwise edge increases.

484, 6660, 91916, 1269036, 17521780, 241927524, 3340355564, 46121153580, 636806710036, 8792555155236, 121401086008460, 1676216233423404, 23143951620064564, 319554533544992100, 4412172198832106156

Offset

1,1

Links

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

Formula

Empirical: a(n) = 16*a(n-1) - 31*a(n-2) + 10*a(n-3).

Empirical g.f.: 4*x*(121 - 271*x + 90*x^2) / (1 - 16*x + 31*x^2 - 10*x^3). - Colin Barker, Oct 16 2018

Example

Some solutions for n=3:
..3..1..3....1..2..3....1..0..3....0..2..3....1..3..0....1..2..3....1..3..1
..2..3..2....2..3..2....0..2..0....3..0..2....0..1..2....3..1..2....3..1..0
..3..1..3....0..2..0....3..0..3....0..1..0....2..0..1....2..3..1....2..0..3
..1..0..1....2..3..2....1..2..0....2..3..2....0..2..3....3..0..3....3..2..0

Crossrefs

Column 2 of A234786.

Sequence in context: A237078 A085120 A250614 * A013771 A114774 A013903

Adjacent sequences: A234777 A234778 A234779 * A234781 A234782 A234783

Keyword

nonn

Author

R. H. Hardin, Dec 30 2013

Status

approved