A173810 a(n) = (8*10^n - 71)/9 for n > 0.

1, 81, 881, 8881, 88881, 888881, 8888881, 88888881, 888888881, 8888888881, 88888888881, 888888888881, 8888888888881, 88888888888881, 888888888888881, 8888888888888881, 88888888888888881, 888888888888888881, 8888888888888888881, 88888888888888888881, 888888888888888888881

Offset: 1

Author

Vincenzo Librandi, Feb 25 2010

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..100
• Index entries for linear recurrences with constant coefficients, signature (11,-10).

Crossrefs

Cf. A092675.

Programs

Magma

[(8*10^n-71)/9: n in [1..20]]; // Vincenzo Librandi, Jul 05 2012

Maple

A173810:=n->(8*10^n-71)/9; seq(A173810(k), k=1..50); # Wesley Ivan Hurt, Nov 05 2013

Mathematica

CoefficientList[Series[x(1+70*x)/((1-x)*(1-10*x)),{x,0,30}],x] (* Vincenzo Librandi, Jul 05 2012 *)
LinearRecurrence[{11,-10},{1,81},30] (* Harvey P. Dale, Feb 20 2016 *)

Formula

a(n) = 10*a(n-1) + 71 for n > 0, a(0) = -7.

From Vincenzo Librandi, Jul 05 2012: (Start)

G.f.: x*(1+70*x)/((1-x)*(1-10*x)).

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

E.g.f.: exp(x)*(8*exp(9*x) - 71)/9. - Elmo R. Oliveira, Sep 09 2024