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A115489
Number of monic irreducible polynomials of degree 3 in GF(2^n)[x].
2
2, 20, 168, 1360, 10912, 87360, 699008, 5592320, 44739072, 357913600, 2863310848, 22906490880, 183251935232, 1466015498240, 11728124018688, 93824992215040, 750599937851392, 6004799503073280, 48038396025110528
OFFSET
1,1
FORMULA
a(0)=0, a(1)=2, a(n)=10a(n-1)-16a(n-2). - T. D. Noe, Nov 30 2006
G.f.: 2*x / ( (8*x-1)*(2*x-1) ). - R. J. Mathar, Jul 23 2014
MATHEMATICA
LinearRecurrence[{10, -16}, {2, 20}, 30] (* Harvey P. Dale, Sep 25 2013 *)
CoefficientList[Series[2/((8 x - 1) (2 x - 1)), {x, 0, 30}], x] (* Vincenzo Librandi, Jul 25 2014 *)
PROG
(Magma) [-(1/3)*2^n+(1/3)*8^n: n in [1..20]]; // Vincenzo Librandi, Jul 25 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Max Alekseyev, Jan 16 2006
STATUS
approved