A173808 a(n) = (7*10^n + 11)/9 for n > 0.

9, 79, 779, 7779, 77779, 777779, 7777779, 77777779, 777777779, 7777777779, 77777777779, 777777777779, 7777777777779, 77777777777779, 777777777777779, 7777777777777779, 77777777777777779, 777777777777777779, 7777777777777777779, 77777777777777777779, 777777777777777777779

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. A093404.

Programs

Magma

[(7*10^n+11)/9: n in [1..20]]; // Vincenzo Librandi Jul 05 2012

Mathematica

CoefficientList[Series[(9-20*x)/((1-x)*(1-10*x)),{x,0,30}],x] (* Vincenzo Librandi, Jul 05 2012 *)
LinearRecurrence[{11,-10},{9,79},30] (* or *) Table[10*FromDigits[PadRight[{},n,7]]+9,{n,0,30}] (* Harvey P. Dale, Dec 03 2024 *)

Formula

a(n) = 10*a(n-1) - 11 with n > 0, a(0)=2.

From Vincenzo Librandi, Jul 05 2012: (Start)

G.f.: x*(9-20*x)/((1-x)*(1-10*x)).

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

E.g.f.: exp(x)*(7*exp(9*x) + 11)/9 - 2. - Elmo R. Oliveira, Sep 09 2024