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 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 (list; graph; refs; listen; history; text; internal format)
 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 Cf. A000045. Cf. A022307, A075735. Sequence in context: A265785 A326372 A001685 * A139589 A152114 A139095 Adjacent sequences:  A074688 A074689 A074690 * A074692 A074693 A074694 KEYWORD easy,nice,nonn AUTHOR Felice Russo, Sep 03 2002 EXTENSIONS More terms from Jani Melik, Oct 07 2002 STATUS approved

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Last modified January 23 13:52 EST 2020. Contains 331171 sequences. (Running on oeis4.)