A074554 a(n) = 3^n + 5^n + 9^n.

3, 17, 115, 881, 7267, 62417, 547795, 4863281, 43443907, 389393297, 3496609075, 31430064881, 282674208547, 2543088125777, 22882900753555, 205921664021681, 1853172819789187, 16677944768259857, 150098450381685235

Offset: 0

Author

Robert G. Wilson v, Aug 23 2002

Keywords

• easy
• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..200
• Index entries for linear recurrences with constant coefficients, signature (17,-87,135).

Crossrefs

Cf. A001550, A001576, A034513, A001579, A074501 - A074580.

Programs

Magma

[3^n + 5^n + 9^n: n in [0..30]]; // Vincenzo Librandi, Jun 13 2011

Mathematica

Table[3^n + 5^n + 9^n, {n, 0, 20}]
LinearRecurrence[{17,-87,135},{3,17,115},30] (* Harvey P. Dale, Nov 27 2012 *)

Formula

From Mohammad K. Azarian, Dec 30 2008: (Start)

G.f.: 1/(1-3*x) + 1/(1-5*x) + 1/(1-9*x).

E.g.f.: exp(3*x) + exp(5*x) + exp(9*x). (End)

a(n) = 17*a(n-1) - 87*a(n-2) + 135*a(n-3).