A209506 Half the number of (n+1) X 4 0..2 arrays with every 2 X 2 subblock having two or four distinct clockwise edge differences.

81, 561, 3906, 27225, 189801, 1323270, 9225765, 64321641, 448447914, 3126561201, 21798261945, 151976626974, 1059575080797, 7387315894233, 51504076597986, 359084401453161, 2503522359474057, 17454459673057014, 121691808074121237

Offset

1,1

Comments

Column 3 of A209511.

Links

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

Formula

Empirical: a(n) = 9*a(n-1) - 15*a(n-2) + 6*a(n-3).

Empirical g.f.: 3*x*(27 - 56*x + 24*x^2) / (1 - 9*x + 15*x^2 - 6*x^3). - Colin Barker, Jul 10 2018

Example

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

Crossrefs

Cf. A209511.

Sequence in context: A186141 A185771 A186133 * A139156 A237035 A237028

Adjacent sequences: A209503 A209504 A209505 * A209507 A209508 A209509

Keyword

nonn

Author

R. H. Hardin, Mar 09 2012

Status

approved