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A133129 Number of black/white colorings of a 3 X n rectangle which have no monochromatic 2 by 2 subsquares. 2
8, 50, 322, 2066, 13262, 85126, 546410, 3507314, 22512862, 144506294, 927561722, 5953863490, 38216853518, 245307588134, 1574588362378, 10107019231634 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..16.

FORMULA

Empirical G.f.: x*(8+2*x-2*x^2)/(1-6*x-3*x^2+2*x^3). - Colin Barker, Jan 04 2012

EXAMPLE

a(2) = 50 because if the middle row is not monochromatic, the top and bottom rows are unconstrained, contributing 2*4*4. if the middle row is monochromatic, the top and bottom rows can each take on only 3 values contributing 2*3*3.

CROSSREFS

Cf. A055099.

Sequence in context: A240050 A221478 A180029 * A103458 A238841 A100310

Adjacent sequences:  A133126 A133127 A133128 * A133130 A133131 A133132

KEYWORD

nonn

AUTHOR

Victor S. Miller, Sep 19 2007

EXTENSIONS

More terms from Colin Barker, Jan 03 2012

STATUS

approved

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Last modified November 28 10:47 EST 2014. Contains 250320 sequences.