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A116530
a(n) = 3*a(n-1), with a(1) = 20.
1
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
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
KEYWORD
nonn,less,easy
AUTHOR
Ben Gregson (mahishimi(AT)hotmail.com), Mar 26 2006
STATUS
approved