A116530 a(n) = 3*a(n-1), with a(1) = 20.

20, 60, 180, 540, 1620, 4860, 14580, 43740, 131220, 393660, 1180980, 3542940, 10628820, 31886460, 95659380, 286978140, 860934420, 2582803260, 7748409780, 23245229340, 69735688020, 209207064060, 627621192180, 1882863576540

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Tanya Khovanova, Recursive Sequences

Index entries for linear recurrences with constant coefficients, signature (3).

Formula

a(n) = 10*A008776(n+1).

G.f.: 20*x/(1-3*x). - Philippe Deléham, Nov 23 2008

From G. C. Greubel, Oct 31 2016: (Start)

a(n) = 20*3^(n-1).

E.g.f.: (20/3)*(exp(3*x) - 1). (End)

Mathematica

Table[4*5*3^(n - 1), {n, 24}] (* Robert G. Wilson v, May 19 2006 *)
LinearRecurrence[{3}, {20}, 25] (* G. C. Greubel, Oct 31 2016 *)

Prog

(Magma) [20*3^(n-1): n in [1..30]]; // Vincenzo Librandi, Oct 31 2016

Crossrefs

Sequence in context: A154072 A078184 A362268 * A219830 A359444 A041780

Adjacent sequences: A116527 A116528 A116529 * A116531 A116532 A116533

Keyword

nonn,less,easy

Author

Ben Gregson (mahishimi(AT)hotmail.com), Mar 26 2006

Status

approved