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A074776
Numbers k such that 2^k-1 and F(k) are not relatively prime, where F(k) denotes the k-th Fibonacci number.
5
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
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.
Subsequences: A079506, A080050.
Sequence in context: A310967 A310968 A289362 * A310969 A153762 A310970
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Sep 07 2002
STATUS
approved