A206661 Number of (n+1) X 2 0..2 arrays with every 2 X 2 subblock having the number of clockwise edge increases equal to the number of counterclockwise edge increases in its adjacent leftward and upward neighbors.

81, 423, 2286, 12477, 68253, 373644, 2046027, 11205045, 61367382, 336102549, 1840818345, 10082134260, 55219849119, 302439528345, 1656464709102, 9072479040225, 49690095904605, 272153381274660, 1490588111370819

Offset

1,1

Comments

Column 1 of A206668.

Links

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

Formula

Empirical: a(n) = 9*a(n-1) - 18*a(n-2) - 19*a(n-3) + 71*a(n-4) - 28*a(n-5) - 22*a(n-6) + 8*a(n-7).

Empirical g.f.: 3*x*(27 - 102*x - 21*x^2 + 352*x^3 - 202*x^4 - 126*x^5 + 56*x^6) / ((1 - x)*(1 - 8*x + 10*x^2 + 29*x^3 - 42*x^4 - 14*x^5 + 8*x^6)). - Colin Barker, Jun 17 2018

Example

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

Crossrefs

Cf. A206668.

Sequence in context: A238180 A206414 A205979 * A238173 A206407 A236610

Adjacent sequences: A206658 A206659 A206660 * A206662 A206663 A206664

Keyword

nonn

Author

R. H. Hardin, Feb 11 2012

Status

approved