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%I #22 Sep 08 2022 08:45:24
%S 20,60,180,540,1620,4860,14580,43740,131220,393660,1180980,3542940,
%T 10628820,31886460,95659380,286978140,860934420,2582803260,7748409780,
%U 23245229340,69735688020,209207064060,627621192180,1882863576540
%N a(n) = 3*a(n-1), with a(1) = 20.
%H Vincenzo Librandi, <a href="/A116530/b116530.txt">Table of n, a(n) for n = 1..1000</a>
%H Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a>
%H <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (3).
%F a(n) = 10*A008776(n+1).
%F G.f.: 20*x/(1-3*x). - _Philippe Deléham_, Nov 23 2008
%F From _G. C. Greubel_, Oct 31 2016: (Start)
%F a(n) = 20*3^(n-1).
%F E.g.f.: (20/3)*(exp(3*x) - 1). (End)
%t Table[4*5*3^(n - 1), {n, 24}] (* _Robert G. Wilson v_, May 19 2006 *)
%t LinearRecurrence[{3},{20},25] (* _G. C. Greubel_, Oct 31 2016 *)
%o (Magma) [20*3^(n-1): n in [1..30]]; // _Vincenzo Librandi_, Oct 31 2016
%K nonn,less,easy
%O 1,1
%A Ben Gregson (mahishimi(AT)hotmail.com), Mar 26 2006
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