login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

T. D. Noe, Table of n, a(n) for n=1..100

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: A056162 A265785 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 19 19:11 EDT 2019. Contains 324222 sequences. (Running on oeis4.)