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A168569 a(n) = 9*(3^n - 1)/2. 2
0, 9, 36, 117, 360, 1089, 3276, 9837, 29520, 88569, 265716, 797157, 2391480, 7174449, 21523356, 64570077, 193710240, 581130729, 1743392196, 5230176597, 15690529800, 47071589409, 141214768236, 423644304717, 1270932914160 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (4,-3).

FORMULA

From R. J. Mathar, Jan 04 2011: (Start)

a(n) = 9*A003462(n).

G.f.: 9*x / ( (3*x-1)*(x-1) ). (End)

a(n) = 4*a(n-1)-3*a(n-2). - Robert Israel, Sep 24 2014

E.g.f.: (9/2)*(exp(3*x) - exp(x)). - G. C. Greubel, Jul 26 2016

MATHEMATICA

9 (3^Range[0, 30]-1)/2  (* Harvey P. Dale, Mar 18 2011 *)

CoefficientList[Series[9 x / ((1 - x) (1 - 3 x)), {x, 0, 30}], x] (* Vincenzo Librandi, Sep 24 2014 *)

PROG

(MAGMA) [9*(3^n-1)/2: n in [0..30]]; // Vincenzo Librandi, Sep 24 2014

(PARI) a(n)=9*(3^n-1)/2 \\ Charles R Greathouse IV, Jul 26 2016

CROSSREFS

Cf. A003462.

Sequence in context: A212104 A193007 A259279 * A213283 A188162 A023872

Adjacent sequences:  A168566 A168567 A168568 * A168570 A168571 A168572

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Nov 30 2009

STATUS

approved

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Last modified May 29 15:44 EDT 2020. Contains 334704 sequences. (Running on oeis4.)