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a(n) = n*8^n - 1.
6

%I #22 Mar 27 2024 11:20:45

%S 7,127,1535,16383,163839,1572863,14680063,134217727,1207959551,

%T 10737418239,94489280511,824633720831,7146825580543,61572651155455,

%U 527765581332479,4503599627370495,38280596832649215,324259173170675711

%N a(n) = n*8^n - 1.

%H Vincenzo Librandi, <a href="/A064754/b064754.txt">Table of n, a(n) for n = 1..1000</a>

%H Paul Leyland, <a href="http://www.leyland.vispa.com/numth/factorization/cullen_woodall/cw.htm">Factors of Cullen and Woodall numbers</a>

%H Paul Leyland, <a href="http://www.leyland.vispa.com/numth/factorization/cullen_woodall/gcw.htm">Generalized Cullen and Woodall numbers</a>

%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (17,-80,64).

%F G.f.: x*(64*x^2 - 8*x - 7)/((x-1)*(8*x-1)^2). - _Colin Barker_, Oct 15 2012

%F 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

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

%o (Magma) [ n*8^n-1: n in [1..20]]; // _Vincenzo Librandi_, Sep 16 2011

%K nonn,easy

%O 1,1

%A _N. J. A. Sloane_, Oct 19 2001