A206087 Number of (n+1) X 2 0..2 arrays with every 2 X 3 or 3 X 2 subblock having exactly two counterclockwise and two clockwise edge increases.

81, 270, 972, 3564, 13608, 52812, 205416, 803844, 3153816, 12375180, 48598056, 190924452, 750064536, 2947003884, 11579514408, 45498547908, 178776400536, 702469087308, 2760220004904, 10845780014052, 42616578679704

Offset

1,1

Comments

Column 1 of A206094.

Links

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

Formula

Empirical: a(n) = 4*a(n-1) - a(n-2) + 12*a(n-3) - 36*a(n-4).

Empirical g.f.: 27*x*(3 - 2*x - x^2 - 38*x^3) / ((1 - 2*x)*(1 - 2*x - 3*x^2 - 18*x^3)). - Colin Barker, Jun 13 2018

Example

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

Crossrefs

Cf. A206094.

Sequence in context: A206094 A202333 A207042 * A236809 A236802 A236875

Adjacent sequences: A206084 A206085 A206086 * A206088 A206089 A206090

Keyword

nonn

Author

R. H. Hardin, Feb 03 2012

Status

approved