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A185513 Number of (n+1) X 2 0..2 arrays with every 2 X 2 subblock singular. 1
31, 143, 593, 2553, 10847, 46303, 197329, 841449, 3587359, 15295151, 65211089, 278030937, 1185395807, 5053987327, 21547889233, 91870352457, 391693178911, 1670000659151, 7120119353681, 30356933960889, 129428088631391 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 1 of A185521.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n) = 4*a(n-1) + 3*a(n-2) - 8*a(n-3).

Empirical g.f.: x*(31 + 19*x - 72*x^2) / (1 - 4*x - 3*x^2 + 8*x^3). - Colin Barker, Apr 16 2018

EXAMPLE

Some solutions for 3 X 2:

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

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

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

CROSSREFS

Cf. A185521.

Sequence in context: A233303 A185521 A228261 * A234122 A142758 A124994

Adjacent sequences:  A185510 A185511 A185512 * A185514 A185515 A185516

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 29 2011

STATUS

approved

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Last modified January 27 06:18 EST 2022. Contains 350601 sequences. (Running on oeis4.)