A074780 Numbers k such that 2^k-1 and F(k) are relatively prime, where F(k) denotes the k-th Fibonacci number.

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

Amiram Eldar, Table of n, a(n) for n = 1..10000

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.

Cf. A000045, A000225.

Sequence in context: A050747 A261514 A215798 * A292938 A056900 A226808

Adjacent sequences: A074777 A074778 A074779 * A074781 A074782 A074783

Keyword

nonn

Author

Benoit Cloitre, Sep 07 2002

Status

approved