OFFSET
0,1
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (12,-27).
FORMULA
From Mohammad K. Azarian, Jan 11 2009: (Start)
G.f.: 1/(1-3*x) + 1/(1-9*x).
E.g.f.: exp(3*x) + exp(9*x). (End)
a(n) = 12*a(n-1) - 27*a(n-2) with a(0)=2, a(1)=12. - Vincenzo Librandi, Jul 21 2010
a(n) = 2*A025551(n). - G. C. Greubel, Jan 13 2024
MATHEMATICA
Table[3^n + 9^n, {n, 0, 25}]
LinearRecurrence[{12, -27}, {2, 12}, 20] (* Harvey P. Dale, May 18 2023 *)
PROG
(Magma) [3^n+9^n: n in [0..30]]; // G. C. Greubel, Jan 13 2024
(SageMath) [3^n+9^n for n in range(31)] # G. C. Greubel, Jan 13 2024
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Robert G. Wilson v, Aug 25 2002
STATUS
approved