A074779 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, 4, 5, 6, 7, 8, 9, 11, 12, 13, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 31, 32, 33, 34, 35, 37, 38, 39, 40, 41, 43, 44, 45, 46, 47, 48, 49, 51, 52, 53, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, 72, 73, 75, 76, 77, 78, 79, 80, 81

Offset

1,2

Links

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

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

Formula

a(n) seems to be asymptotic to c*n with c = 1.207...

Mathematica

Select[Range[100], CoprimeQ[2^# + 1, Fibonacci[#]] &] (* Amiram Eldar, May 08 2022 *)

Crossrefs

Cf. A000045, A000051.

Sequence in context: A030700 A305933 A105208 * A253567 A048197 A253784

Adjacent sequences: A074776 A074777 A074778 * A074780 A074781 A074782

Keyword

nonn

Author

Benoit Cloitre, Sep 07 2002

Status

approved