A064755 a(n) = n*9^n - 1.
8, 161, 2186, 26243, 295244, 3188645, 33480782, 344373767, 3486784400, 34867844009, 345191655698, 3389154437771, 33044255768276, 320275094369453, 3088366981419734, 29648323021629455, 283512088894331672, 2701703435345984177, 25666182635786849690, 243153309181138576019
Offset: 1
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..1000
- Paul Leyland, Factors of Cullen and Woodall numbers.
- Paul Leyland, Generalized Cullen and Woodall numbers.
- Index entries for linear recurrences with constant coefficients, signature (19,-99,81).
Programs
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Magma
[ n*9^n-1: n in [1..20]]; // Vincenzo Librandi, Sep 16 2011
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Mathematica
Table[n*9^n-1,{n,20}] (* Harvey P. Dale, Feb 28 2017 *)
Formula
From Chai Wah Wu, Feb 01 2018: (Start)
a(n) = 19*a(n-1) - 99*a(n-2) + 81*a(n-3) for n > 3.
G.f.: x*(81*x^2 - 9*x - 8)/((x - 1)*(9*x - 1)^2). (End)
From Elmo R. Oliveira, May 05 2025: (Start)
E.g.f.: 1 + exp(x)*(9*x*exp(8*x) - 1).
a(n) = A158749(n) - 1. (End)