A074545 a(n) = 2^n + 7^n + 9^n.

3, 18, 134, 1080, 8978, 75888, 649154, 5606640, 48811778, 427774608, 3769260674, 33358388400, 296270827778, 2638754846928, 23555015544194, 210638693637360, 1886253119486978, 16909812213784848, 151723048895171714

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 (18,-95,126).

Crossrefs

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

Programs

Magma

[ 2^n + 7^n + 9^n: n in [0..30]]; // Vincenzo Librandi, Jun 13 2011

Mathematica

Table[2^n + 7^n + 9^n, {n, 0, 20}]
LinearRecurrence[{18,-95,126},{3,18,134},20] (* Harvey P. Dale, Apr 13 2019 *)

Formula

From Mohammad K. Azarian, Dec 28 2008: (Start)

G.f.: 1/(1-2*x) + 1/(1-7*x) + 1/(1-9*x).

E.g.f.: exp(2*x) + exp(7*x) + exp(9*x). (End)

a(n) = 18*a(n-1) - 95*a(n-2) + 126*a(n-3).