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

Offset

1,1

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).

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

Mathematica

Table[n*8^n-1, {n, 20}] (* or *) LinearRecurrence[{17, -80, 64}, {7, 127, 1535}, 20] (* Harvey P. Dale, May 20 2013 *)

Prog

(Magma) [ n*8^n-1: n in [1..20]]; // Vincenzo Librandi, Sep 16 2011

Crossrefs

Sequence in context: A088550 A255954 A278791 * A267249 A025166 A241955

Adjacent sequences: A064751 A064752 A064753 * A064755 A064756 A064757

Keyword

nonn,easy

Author

N. J. A. Sloane, Oct 19 2001

Status

approved