A173812 a(n) = (8*10^n - 17)/9 for n > 0.

7, 87, 887, 8887, 88887, 888887, 8888887, 88888887, 888888887, 8888888887, 88888888887, 888888888887, 8888888888887, 88888888888887, 888888888888887, 8888888888888887, 88888888888888887, 888888888888888887, 8888888888888888887, 88888888888888888887, 888888888888888888887

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..100

Index entries for linear recurrences with constant coefficients, signature (11,-10).

Formula

a(n) = 10*a(n-1) + 17 with n > 0, a(0)=-1.

From Vincenzo Librandi, Jul 05 2012: (Start)

a(n) = 11*a(n-1) - 10*a(n-2) for n > 2.

G.f.: x*(7+10*x)/((1-x)*(1-10*x)). (End)

E.g.f.: 1 + exp(x)*(8*exp(9*x) - 17)/9. - Elmo R. Oliveira, Sep 09 2024

Mathematica

CoefficientList[Series[(7+10*x)/((1-x)*(1-10*x)), {x, 0, 30}], x] (* Vincenzo Librandi, Jul 05 2012 *)
Table[FromDigits[PadLeft[{7}, n, 8]], {n, 20}] (* Harvey P. Dale, Jun 22 2013 *)

Prog

(Magma) [(8*10^n-17)/9: n in [1..20]]; // Vincenzo Librandi, Jul 05 2012

Crossrefs

Cf. A093171.

Sequence in context: A183613 A295036 A295527 * A199027 A360237 A279845

Adjacent sequences: A173809 A173810 A173811 * A173813 A173814 A173815

Keyword

nonn,easy

Author

Vincenzo Librandi, Feb 25 2010

Status

approved