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A074780
Numbers k such that 2^k-1 and F(k) are relatively prime, where F(k) denotes the k-th Fibonacci number.
2
1, 2, 3, 5, 6, 7, 9, 13, 14, 15, 17, 19, 21, 23, 25, 26, 27, 29, 31, 34, 35, 37, 38, 39, 41, 42, 43, 45, 46, 47, 49, 51, 53, 57, 59, 61, 62, 63, 65, 67, 69, 71, 73, 74, 75, 79, 81, 82, 83, 85, 86, 87, 89, 91, 93, 94, 95, 97, 98, 101, 102, 103, 105, 106, 107, 109, 111, 113
OFFSET
1,2
LINKS
FORMULA
a(n) seems to be asymptotic to c*n with c=1.7...
MATHEMATICA
Select[Range[120], CoprimeQ[2^#-1, Fibonacci[#]]&] (* Harvey P. Dale, Nov 27 2015 *)
CROSSREFS
Complement of A074776.
Sequence in context: A050747 A261514 A215798 * A292938 A056900 A226808
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Sep 07 2002
STATUS
approved