A074776 Numbers k such that 2^k-1 and F(k) are not relatively prime, where F(k) denotes the k-th Fibonacci number.

4, 8, 10, 11, 12, 16, 18, 20, 22, 24, 28, 30, 32, 33, 36, 40, 44, 48, 50, 52, 54, 55, 56, 58, 60, 64, 66, 68, 70, 72, 76, 77, 78, 80, 84, 88, 90, 92, 96, 99, 100, 104, 108, 110, 112, 116, 120, 121, 124, 126, 128, 130, 132, 136, 138, 140, 143, 144, 148, 150, 152, 154

Offset

1,1

Links

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

Formula

a(n) seems to be asymptotic to c*n with c=2.2...

Mathematica

Select[Range[100], !CoprimeQ[2^# - 1, Fibonacci[#]] &] (* Amiram Eldar, Aug 29 2020 *)

Prog

(PARI) isok(n)=gcd(2^n-1, fibonacci(n)) != 1 \\ Edward Jiang, Sep 06 2014

Crossrefs

Complement of A074780.

Cf. A000045, A000225.

Subsequences: A079506, A080050.

Sequence in context: A310967 A310968 A289362 * A310969 A153762 A310970

Adjacent sequences: A074773 A074774 A074775 * A074777 A074778 A074779

Keyword

nonn

Author

Benoit Cloitre, Sep 07 2002

Status

approved