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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. 1
24, 78, 228, 722, 2136, 6688, 19976, 62048, 186560, 576288, 1740672, 5356544, 16230528, 49815040, 151270400, 463442432, 1409423360, 4312621056, 13129156608, 40138661888, 122283737088, 373625921536, 1138824544256, 3478142320640 (list; graph; refs; listen; history; text; internal format)
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 A068379

Adjacent sequences:  A206000 A206001 A206002 * A206004 A206005 A206006

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 02 2012

STATUS

approved

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Last modified February 25 20:04 EST 2020. Contains 332258 sequences. (Running on oeis4.)