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A198966
a(n) = 8*9^n-1.
3
7, 71, 647, 5831, 52487, 472391, 4251527, 38263751, 344373767, 3099363911, 27894275207, 251048476871, 2259436291847, 20334926626631, 183014339639687, 1647129056757191, 14824161510814727, 133417453597332551, 1200757082375992967
OFFSET
0,1
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
MATHEMATICA
CoefficientList[Series[(7 + x)/(1 - 10*x + 9*x^2), {x, 0, 30}], x] (* Vincenzo Librandi, Jan 03 2013 *)
PROG
(Magma) [8*9^n-1: n in [0..20]]
(PARI) a(n) = 8*9^n - 1; \\ Michel Marcus, Feb 03 2016
CROSSREFS
Sequence in context: A196742 A196900 A319963 * A069591 A039920 A100895
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 01 2011
STATUS
approved