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A214091 a(n) = 3^n - 2^(n+2). 3
-3, -5, -7, -5, 17, 115, 473, 1675, 5537, 17635, 54953, 168955, 515057, 1561555, 4717433, 14217835, 42784577, 128615875, 386371913, 1160164315, 3482590097, 10451964595, 31364282393, 94109624395, 282362427617, 847154391715, 2541597392873, 7625060614075, 22875718713137 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

The subsequence of (positive or negative) primes begins: -3, -5, -7, -5, 17, no more through the composite a(116) (which is near 2.2*10^55). - Jonathan Vos Post, Jul 03 2012

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (5,-6).

FORMULA

G.f.: ( -3+10*x ) / ( (3*x-1)*(2*x-1) ). - R. J. Mathar, Jul 07 2012

a(n) = 5*a(n-1) - 6*a(n-2) for n>1. - Vincenzo Librandi, Jun 18 2014

MATHEMATICA

Table[3^n - 2^(n+2), {n, 0, 30}] (* or *) CoefficientList[Series[(-3 + 10 x)/((3 x - 1) (2 x - 1)), {x, 0, 30}], x] (* Vincenzo Librandi, Jun 17 2014 *)

PROG

(MAGMA) [3^n - 2^(n+2): n in [0..30]]; // Vincenzo Librandi, Jun 18 2014

CROSSREFS

Cf. A001047 (3^n - 2^n), A003063 (3^n - 2^(n+1)).

Sequence in context: A256258 A177433 A264827 * A071581 A184722 A219781

Adjacent sequences:  A214088 A214089 A214090 * A214092 A214093 A214094

KEYWORD

sign,easy

AUTHOR

Alex Ratushnyak, Jul 03 2012

STATUS

approved

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Last modified November 11 18:50 EST 2019. Contains 329031 sequences. (Running on oeis4.)