A198966 a(n) = 8*9^n-1.

7, 71, 647, 5831, 52487, 472391, 4251527, 38263751, 344373767, 3099363911, 27894275207, 251048476871, 2259436291847, 20334926626631, 183014339639687, 1647129056757191, 14824161510814727, 133417453597332551, 1200757082375992967

Offset: 0

Author

Vincenzo Librandi, Nov 01 2011

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (10,-9).

Programs

Magma

[8*9^n-1: n in [0..20]]

Mathematica

CoefficientList[Series[(7 + x)/(1 - 10*x + 9*x^2), {x, 0, 30}], x] (* Vincenzo Librandi, Jan 03 2013 *)

PARI

a(n) = 8*9^n - 1; \\ Michel Marcus, Feb 03 2016

Formula

a(n) = 9*a(n-1)+8. a(n) = 10*a(n-1)-9*a(n-2), n>1.

G.f.: (7 + x)/(1 - 10*x + 9*x^2). - Vincenzo Librandi, Jan 03 2013