A064754 a(n) = n*8^n - 1.
7, 127, 1535, 16383, 163839, 1572863, 14680063, 134217727, 1207959551, 10737418239, 94489280511, 824633720831, 7146825580543, 61572651155455, 527765581332479, 4503599627370495, 38280596832649215, 324259173170675711, 2738188573441261567, 23058430092136939519
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 (17,-80,64).
Programs
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Magma
[ n*8^n-1: n in [1..20]]; // Vincenzo Librandi, Sep 16 2011
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Mathematica
Table[n*8^n-1,{n,20}] (* or *) LinearRecurrence[{17,-80,64},{7,127,1535},20] (* Harvey P. Dale, May 20 2013 *)
Formula
G.f.: x*(64*x^2 - 8*x - 7)/((x-1)*(8*x-1)^2). - Colin Barker, Oct 15 2012
a(n) = 17*a(n-1) - 80*a(n-2) + 64*a(n-3); a(1)=7, a(2)=127, a(3)=1535. - Harvey P. Dale, May 20 2013
From Elmo R. Oliveira, May 05 2025: (Start)
E.g.f.: 1 + exp(x)*(8*x*exp(7*x) - 1).
a(n) = A036294(n) - 1. (End)