A155607 9^n+3^n-1.

1, 11, 89, 755, 6641, 59291, 532169, 4785155, 43053281, 387440171, 3486843449, 31381236755, 282430067921, 2541867422651, 22876797237929, 205891146443555, 1853020231898561, 16677181828806731, 150094635684419609

Offset

0,2

Links

Table of n, a(n) for n=0..18.

Index entries for linear recurrences with constant coefficients, signature (13,-39,27).

Formula

G.f.: 1/(1-9*x)+1/(1-3*x)-1/(1-x). E.g.f.: e^(9*x)+e^(3*x)-e^x.

a(n)=12*a(n-1)-27*a(n-2)-16 with a(0)=1, a(1)=11 - Vincenzo Librandi, Jul 21 2010

Mathematica

LinearRecurrence[{13, -39, 27}, {1, 11, 89}, 20] (* Harvey P. Dale, Dec 29 2018 *)

Prog

(PARI) a(n)=9^n+3^n-1 \\ Charles R Greathouse IV, Jun 11 2015

Crossrefs

Cf. A155596, A155597, A155598, A155599, A155600, A155601, A155602, A155603, A155604, A155605, A155606.

Sequence in context: A081657 A226854 A037580 * A356323 A110252 A199394

Adjacent sequences: A155604 A155605 A155606 * A155608 A155609 A155610

Keyword

nonn,easy

Author

Mohammad K. Azarian, Jan 25 2009

Status

approved