A206003 Number of (n+1) X 2 0..2 arrays with the number of clockwise edge increases in every 2 X 2 subblock equal to one, and every 2 X 2 determinant nonzero.

24, 78, 228, 722, 2136, 6688, 19976, 62048, 186560, 576288, 1740672, 5356544, 16230528, 49815040, 151270400, 463442432, 1409423360, 4312621056, 13129156608, 40138661888, 122283737088, 373625921536, 1138824544256, 3478142320640

Offset

1,1

Comments

Column 1 of A206010.

Links

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

Formula

Empirical: a(n) = 8*a(n-2) + 4*a(n-3) for n>4.

Empirical g.f.: 2*x*(12 + 39*x + 18*x^2 + x^3) / (1 - 8*x^2 - 4*x^3). - Colin Barker, Jun 13 2018

Example

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

Crossrefs

Cf. A206010.

Sequence in context: A290710 A206010 A124140 * A143839 A114818 A190102

Adjacent sequences: A206000 A206001 A206002 * A206004 A206005 A206006

Keyword

nonn

Author

R. H. Hardin, Feb 02 2012

Status

approved