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
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 30 2009
STATUS
approved