A198699 a(n) = 7*10^n - 1.
6, 69, 699, 6999, 69999, 699999, 6999999, 69999999, 699999999, 6999999999, 69999999999, 699999999999, 6999999999999, 69999999999999, 699999999999999, 6999999999999999, 69999999999999999, 699999999999999999, 6999999999999999999, 69999999999999999999, 699999999999999999999
Offset: 0
Links
- Vincenzo Librandi, Table of n, a(n) for n = 0..200
- Index entries for linear recurrences with constant coefficients, signature (11,-10).
Programs
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Magma
[7*10^n-1: n in [0..30]];
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Mathematica
NestList[10#+9&,6,20] (* or *) LinearRecurrence[{11,-10},{6,69},20] (* Harvey P. Dale, Dec 29 2013 *)
Formula
a(n) = 10*a(n-1) + 9.
a(n) = 11*a(n-1) - 10*a(n-2), n>1.
G.f.: (6+3*x)/((10*x-1)*(x-1)). - R. J. Mathar, Oct 29 2011
From Elmo R. Oliveira, Jun 14 2025: (Start)
E.g.f.: exp(x)*(7*exp(9*x) - 1).
a(n) = 3*A198972(n). (End)