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A205991 Number of (n+1) X 2 0..2 arrays with the number of clockwise edge increases in every 2 X 2 subblock equal to two, and every 2 X 2 determinant nonzero. 1
26, 92, 330, 1184, 4250, 15252, 54738, 196448, 705026, 2530252, 9080754, 32589688, 116960298, 419755820, 1506450938, 5406463248, 19403117738, 69635353188, 249912538754, 896904721104, 3218878423314, 11552150479772, 41459217515106 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 1 of A205998.

LINKS

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

FORMULA

Empirical: a(n) = 2*a(n-1) + 5*a(n-2) + 3*a(n-3) - 2*a(n-4) + a(n-5).

Empirical g.f.: 2*x*(13 + 20*x + 8*x^2 - 7*x^3 + 4*x^4) / (1 - 2*x - 5*x^2 - 3*x^3 + 2*x^4 - x^5). - Colin Barker, Jun 13 2018

EXAMPLE

Some solutions for n=4:

..1..0....1..2....2..2....1..1....2..0....2..0....2..1....1..2....2..0....0..1

..2..1....1..0....1..0....0..2....1..2....1..2....0..2....0..1....0..1....2..2

..1..2....2..1....2..1....1..0....0..1....1..0....1..0....2..2....2..2....1..0

..2..1....0..2....1..2....2..1....1..2....0..1....2..1....1..0....1..0....2..1

..1..2....2..1....0..2....0..2....1..0....1..0....1..0....2..1....0..2....0..2

CROSSREFS

Cf. A205998.

Sequence in context: A044213 A044594 A205998 * A259291 A038654 A010014

Adjacent sequences:  A205988 A205989 A205990 * A205992 A205993 A205994

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 02 2012

STATUS

approved

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Last modified April 18 07:39 EDT 2021. Contains 343084 sequences. (Running on oeis4.)