login
A074691
Squarefree Fibonacci numbers with odd number of prime factors.
5
2, 3, 5, 13, 89, 233, 610, 987, 1597, 10946, 28657, 514229, 3524578, 9227465, 24157817, 39088169, 63245986, 433494437, 701408733, 1134903170, 1836311903, 2971215073, 7778742049, 20365011074, 365435296162, 591286729879
OFFSET
1,1
COMMENTS
Agrees for a long time with sequence of Fibonacci numbers whose number of divisors is a Fibonacci number.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..575 (terms 1..100 from T. D. Noe)
FORMULA
Fibonacci(n) such that mu(Fibonacci(n)) = -1, where mu(n) is the Moebius mu function (A008683).
EXAMPLE
610 belongs to the sequence because it has 3 prime factors (2, 5, 61); it also has 8 divisors (1, 2, 5, 10, 61, 122, 305, 610).
MAPLE
with(combinat, fibonacci): m2_fib := proc(n); if (numtheory[mobius](fibonacci(n))=-1) then RETURN(fibonacci(n)); fi; end: seq(m2_fib(i), i=1..100);
MATHEMATICA
Select[Fibonacci[Range[80]], MoebiusMu[#] == -1 &] (* Harvey P. Dale, Aug 23 2011 *)
CROSSREFS
Subsequence of A061305 (squarefree Fibonacci numbers).
Cf. A000045.
Sequence in context: A265785 A326372 A001685 * A139589 A152114 A139095
KEYWORD
easy,nice,nonn
AUTHOR
Felice Russo, Sep 03 2002
EXTENSIONS
More terms from Jani Melik, Oct 07 2002
STATUS
approved