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A115098 a(0)=2, a(n)=3*a(n-1)-3. 3
2, 3, 6, 15, 42, 123, 366, 1095, 3282, 9843, 29526, 88575, 265722, 797163, 2391486, 7174455, 21523362, 64570083, 193710246, 581130735, 1743392202, 5230176603, 15690529806, 47071589415, 141214768242, 423644304723, 1270932914166 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

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

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

FORMULA

a(n) = (3^n+3)/2.

a(n) = A067771(n-1), n>0. [R. J. Mathar, Aug 11 2008]

G.f.: (2-5*x)/((1-x)*(1-3*x)). - Vincenzo Librandi, Sep 13 2014

EXAMPLE

a(4) = (3^4+3)/2 = 84/2 = 42 = 3*a(3)-3 = 3*15-3.

MAPLE

seq((3^i+3)/2, i=0..30);

MATHEMATICA

CoefficientList[Series[(2 - 5 x)/((1 - x) (1 - 3 x)), {x, 0, 40}], x] (* Vincenzo Librandi, Sep 13 2014 *)

NestList[3#-3&, 2, 30] (* Harvey P. Dale, Feb 05 2021 *)

PROG

(MAGMA) [(3^n+3)/2: n in [0..30]]; // Vincenzo Librandi, Sep 13 2014

(PARI) a(n)=(3^n+3)/2 \\ Charles R Greathouse IV, Sep 13 2014

CROSSREFS

Cf. A067771.

Sequence in context: A147773 A006403 A129960 * A036418 A120589 A110181

Adjacent sequences:  A115095 A115096 A115097 * A115099 A115100 A115101

KEYWORD

easy,nonn

AUTHOR

Miklos Kristof, Mar 02 2006

STATUS

approved

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Last modified July 25 03:36 EDT 2021. Contains 346282 sequences. (Running on oeis4.)