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A158749 a(n) = n * 9^n. 1
0, 9, 162, 2187, 26244, 295245, 3188646, 33480783, 344373768, 3486784401, 34867844010, 345191655699, 3389154437772, 33044255768277, 320275094369454, 3088366981419735, 29648323021629456, 283512088894331673 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
FORMULA
a(n) = n*9^n.
a(n) = 18*a(n-1)-81*a(n-2) = A038299(n,1). G.f.: 9x/(1-9x)^2. - R. J. Mathar, Mar 26 2009
a(n) = A001019(n)*n. - Omar E. Pol, Mar 26 2009
From Amiram Eldar, Jul 20 2020: (Start)
Sum_{n>=1} 1/a(n) = log(9/8).
Sum_{n>=1} (-1)^(n+1)/a(n) = log(10/9). (End)
MATHEMATICA
Table[n 9^n, {n, 0, 20}] (* Vincenzo Librandi, Feb 25 2014 *)
PROG
(PARI) a(n) = n*9^n; \\ Joerg Arndt, Feb 23 2014
(Magma) [n*9^n: n in [0..20]]; // Vincenzo Librandi, Feb 25 2014
CROSSREFS
Sequence in context: A319197 A209962 A084874 * A300843 A133681 A157553
KEYWORD
nonn,easy
AUTHOR
Zerinvary Lajos, Mar 25 2009
STATUS
approved

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Last modified June 22 06:24 EDT 2024. Contains 373565 sequences. (Running on oeis4.)