OFFSET
1,2
COMMENTS
Prime for n = 2, 4, 5, 11, 28, 35, no more < 100.
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (5, -8, 4).
FORMULA
a(n) = A000337(n) - 2.
From R. J. Mathar, Jul 26 2009: (Start)
a(n) = 5*a(n-1) - 8*a(n-2) + 4*a(n-3).
G.f.: x*(1-8*x+8*x^2)/((x-1)*(-1+2*x)^2). (End)
EXAMPLE
a(28) = ((2^(28))*(28 - 1)) - 1 = 7247757311.
MATHEMATICA
LinearRecurrence[{5, -8, 4}, {-1, 3, 15}, 100] (* G. C. Greubel, Dec 20 2016 *)
PROG
(PARI) Vec(x*(1-8*x+8*x^2)/((x-1)*(-1+2*x)^2) + O(x^50)) \\ G. C. Greubel, Dec 20 2016
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Jonathan Vos Post, Jul 25 2009
STATUS
approved