A199490 a(n) = (11*7^n + 1)/3.

4, 26, 180, 1258, 8804, 61626, 431380, 3019658, 21137604, 147963226, 1035742580, 7250198058, 50751386404, 355259704826, 2486817933780, 17407725536458, 121854078755204, 852978551286426, 5970849859004980, 41795949013034858, 292571643091244004, 2048001501638708026

Offset

0,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (8,-7).

Formula

a(n) = 7*a(n-1) - 2.

a(n) = 8*a(n-1) - 7*a(n-2).

G.f.: 2*(2-3*x)/((1-x)*(1-7*x)).

From Elmo R. Oliveira, May 09 2025: (Start)

E.g.f.: exp(x)*(1 + 11*exp(6*x))/3.

a(n) = 2*A199489(n) = A199492(n)/3. (End)

Mathematica

\(11 7^Range[0, 20]+1)/3 (* Harvey P. Dale, Aug 01 2020 *)
(* Alternative: *)
LinearRecurrence[{8, -7}, {4, 26}, 20] (* Harvey P. Dale, Aug 01 2020 *)

Prog

(Magma) [(11*7^n+1)/3: n in [0..30]];

Crossrefs

Cf. A199489, A199492.

Sequence in context: A278416 A108082 A390424 * A116429 A392431 A084134

Adjacent sequences: A199487 A199488 A199489 * A199491 A199492 A199493

Keyword

nonn,easy,changed

Author

Vincenzo Librandi, Nov 07 2011

Status

approved