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A061305 Squarefree Fibonacci numbers. 9
1, 1, 2, 3, 5, 13, 21, 34, 55, 89, 233, 377, 610, 987, 1597, 4181, 6765, 10946, 17711, 28657, 121393, 196418, 317811, 514229, 1346269, 2178309, 3524578, 5702887, 9227465, 24157817, 39088169, 63245986, 102334155, 165580141, 433494437, 701408733, 1134903170, 1836311903 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Union of A074691 and A075735. - R. J. Mathar, Feb 06 2010

About 60% of entries are of the form 4k+1; 20% are of the form 4k+2; 20% are of the form 4k+3. Obviously no term is divisible by 4. - Carmine Suriano, Feb 27 2014

Contains A030426 as a subsequence unless there exist Wall-Sun-Sun primes. - Max Alekseyev, Jan 04 2018

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..1080 (terms 1..200 from Zak Seidov)

FORMULA

Set difference of A000045 and A061899. a(n) = A000045(A037918(n)). - R. J. Mathar, Feb 16 2010

EXAMPLE

55 = 5 * 11 is a squarefree Fibonacci number.

MATHEMATICA

a={}; Do[f=Fibonacci[n]; If[SquareFreeQ[f], AppendTo[a, f]], {n, 1, 50}]; a (* Vladimir Joseph Stephan Orlovsky, Jul 22 2008 *)

PROG

(PARI) { n=0; g=0; f=1; for (i=1, 500, if (issquarefree(g), write("b061305.txt", n++, " ", g)); if (n==200, break); s=f; f+=g; g=s ) } \\ Harry J. Smith, Jul 21 2009

CROSSREFS

Cf. A000045.

Sequence in context: A173830 A224223 A238497 * A177374 A142881 A163159

Adjacent sequences:  A061302 A061303 A061304 * A061306 A061307 A061308

KEYWORD

nonn,easy,changed

AUTHOR

Amarnath Murthy, Apr 26 2001

EXTENSIONS

More terms from Asher Natan Auel (auela(AT)reed.edu), May 14 2001

Mathematica updated by Jean-Fran├žois Alcover, Jul 04 2013

STATUS

approved

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Last modified October 22 07:29 EDT 2019. Contains 328315 sequences. (Running on oeis4.)