A198644 a(n) = 8*3^n - 1.

7, 23, 71, 215, 647, 1943, 5831, 17495, 52487, 157463, 472391, 1417175, 4251527, 12754583, 38263751, 114791255, 344373767, 1033121303, 3099363911, 9298091735, 27894275207, 83682825623, 251048476871, 753145430615, 2259436291847, 6778308875543, 20334926626631, 61004779879895

Offset: 0

Author

Vincenzo Librandi, Oct 28 2011

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (4,-3).

Crossrefs

Cf. A199111.

Programs

Magma

[8*3^n-1: n in [0..30]];

Mathematica

8*3^Range[0,30]-1 (* or *) LinearRecurrence[{4,-3},{7,23},30] (* Harvey P. Dale, Jun 16 2024 *)

Formula

a(n) = 3*a(n-1) + 2, a(0)=7.

G.f.: (7-5*x)/((3*x-1)*(x-1)). - R. J. Mathar, Oct 30 2011

From Elmo R. Oliveira, May 07 2025: (Start)

E.g.f.: exp(x)*(8*exp(2*x) - 1).

a(n) = 4*a(n-1) - 3*a(n-2).

a(n) = A199111(n) - 2. (End)