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A126431
a(n) = n*10^n.
9
0, 10, 200, 3000, 40000, 500000, 6000000, 70000000, 800000000, 9000000000, 100000000000, 1100000000000, 12000000000000, 130000000000000, 1400000000000000, 15000000000000000, 160000000000000000, 1700000000000000000, 18000000000000000000, 190000000000000000000
OFFSET
0,2
FORMULA
a(0)=0, a(1)=10; for n > 1, a(n) = 20*a(n-1) - 100*a(n-2). - Harvey P. Dale, Mar 30 2012
G.f.: 10*x/(1 - 10*x)^2. - Vincenzo Librandi, Sep 09 2014
From Amiram Eldar, Jul 20 2020: (Start)
Sum_{n>=1} 1/a(n) = log(10/9).
Sum_{n>=1} (-1)^(n+1)/a(n) = log(11/10). (End)
From Elmo R. Oliveira, Sep 07 2024: (Start)
E.g.f.: 10*x*exp(10*x).
a(n) = n*A011557(n). (End)
MAPLE
A126431 := proc(n) n*10^n ; end proc: # Bruno Berselli, Sep 09 2014
MATHEMATICA
Table[n 10^n, {n, 0, 20}] (* or *) LinearRecurrence[{20, -100}, {0, 10}, 20] (* Harvey P. Dale, Mar 30 2012 *)
CoefficientList[Series[10 x/(1 - 10 x)^2, {x, 0, 20}], x] (* Vincenzo Librandi, Sep 09 2014 *)
PROG
(Magma) [n*10^n: n in [0..20]]; // Vincenzo Librandi, Sep 09 2014
(PARI) a(n)=n*10^n \\ Charles R Greathouse IV, Oct 07 2015
CROSSREFS
Cf. A011557.
Sequence in context: A079436 A285021 A354410 * A335649 A202436 A320671
KEYWORD
nonn,easy
AUTHOR
Jonathan R. Love (japanada11(AT)yahoo.ca), Mar 11 2007
STATUS
approved