

A001605


Indices of prime Fibonacci numbers.
(Formerly M2309 N0911)


97



3, 4, 5, 7, 11, 13, 17, 23, 29, 43, 47, 83, 131, 137, 359, 431, 433, 449, 509, 569, 571, 2971, 4723, 5387, 9311, 9677, 14431, 25561, 30757, 35999, 37511, 50833, 81839, 104911, 130021, 148091, 201107, 397379, 433781, 590041, 593689, 604711, 931517, 1049897, 1285607, 1636007, 1803059, 1968721, 2904353, 3244369
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OFFSET

1,1


COMMENTS

Some of the larger entries may only correspond to probable primes.
Since F(n) divides F(mn) (cf. A001578, A086597), all terms of this sequence are primes except for a(2) = 4 = 2 * 2 but F(2) = 1.  M. F. Hasler, Dec 12 2007
What is the next larger twin prime after F(4) = 3, F(5) = 5, F(7) = 13? The next candidates seem to be F(104911) or F(1968721) (greater of a pair), or F(397379), F(931517) (lesser of a pair).  M. F. Hasler, Jan 30 2013, edited Dec 24 2016, edited Sep 23 2017 by Bobby Jacobs
Henri Lifchitz confirms that the data section gives the full list (49 terms) as far as we know it today of indices of prime Fibonacci numbers (including proven primes and PRPs).  N. J. A. Sloane, Jul 09 2016
Terms n such that n2 is also a term are listed in A279795.  M. F. Hasler, Dec 24 2016
There are no Fibonacci numbers that are twin primes after F(7) = 13. Every Fibonacci prime greater than F(4) = 3 is of the form F(2*n+1). Since F(2*n+1)+2 and F(2*n+1)2 are F(n+2)*L(n1) and F(n1)*L(n+2) in some order, and F(n+2) > 1, L(n1) > 1, F(n1) > 1, and L(n+2) > 1 for n > 3, there are no other Fibonacci twin primes.  Bobby Jacobs, Sep 23 2017


REFERENCES

Clifford A. Pickover, Mazes for the Mind, St. Martin's Press, NY, 1992, p. 350.
Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005; see p. 54.
Paulo Ribenboim, The Little Book of Big Primes, SpringerVerlag, NY, 1991, p. 178.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

Henri Lifchitz, Table of n, a(n) for n = 1..50
J. Brillhart, P. L. Montgomery and R. D. Silverman, Tables of Fibonacci and Lucas factorizations, Math. Comp. 50 (1988), 251260.
David Broadhurst, Fibonacci Numbers
David Broadhurst, Proof that F(81839) is prime, NMBRTHRY Mailing List, 22 April 2001
Chris K. Caldwell, The Prime Glossary, Fibonacci prime
Rosina Campbell, Duc Van Huynh, Tyler Melton, Andrew Percival, Elliptic Curves of Fibonacci order over F_p, arXiv:1710.05687 [math.NT], 2017.
H. Dubner and W. Keller, New Fibonacci and Lucas Primes, Math. Comp. 68 (1999) 417427.
Dudley Fox, Search for Possible Fibonacci Primes
Dov Jarden, Recurring Sequences, Riveon Lematematika, Jerusalem, 1966. [Annotated scanned copy] See p. 36.
Ron Knott, Mathematics of the Fibonacci Series
Henri & Renaud Lifchitz, PRP Records.
Tony D. Noe and Jonathan Vos Post, Primes in Fibonacci nstep and Lucas nstep Sequences, J. of Integer Sequences, Vol. 8 (2005), Article 05.4.4
R. Ondrejka, The Top Ten: a Catalogue of Primal Configurations
PRP Top Records, Search for: F(n)
Eric Weisstein's World of Mathematics, Fibonacci Prime
Eric Weisstein's World of Mathematics, Integer Sequence Primes


FORMULA

Prime(i) = a(n) for some n <=> A080345(i) <= 1.  M. F. Hasler, Dec 12 2007
a(n) = 1 + Sum_{m=1..L(n)} (abs(nS(m))  abs(nS(m)1/2) + 1/2), where S(m) = Sum_{k=1..m} (A010051(A000045(k))) and L(n) >= a(n)  1. L(n) can be any function of n which satisfies the inequality.  Timothy Hopper, Jun 07 2015


MATHEMATICA

Select[Range[10^4], PrimeQ[Fibonacci[#]] &] (* Harvey P. Dale, Nov 20 2012 *)
(* Start ~ 1.8x faster than the above *)
Select[Range[10^4], PrimeQ[#] && PrimeQ[Fibonacci[#]] &] (* Eric W. Weisstein, Nov 07 2017 *)
Select[Prime[Range[PrimePi[10^4]]], PrimeQ[Fibonacci[#]] &] (* Eric W. Weisstein, Nov 07 2017 *)
(* End *)


PROG

(PARI) v=[3, 4]; forprime(p=5, 1e5, if(ispseudoprime(fibonacci(p)), v=concat(v, p))); v \\ Charles R Greathouse IV, Feb 14 2011
(PARI) is_A001605(n)={n==4  isprime(n) & ispseudoprime(fibonacci(n))} \\ M. F. Hasler, Sep 29 2012


CROSSREFS

Cf. A000045, A001578, A005478, A080345, A086597, A117595.
Subsequence of A046022.
Sequence in context: A081735 A227231 A107036 * A216570 A101762 A139455
Adjacent sequences: A001602 A001603 A001604 * A001606 A001607 A001608


KEYWORD

nonn,hard,nice,changed


AUTHOR

N. J. A. Sloane


EXTENSIONS

Additional comments from Robert G. Wilson v, Aug 18 2000
More terms from David Broadhurst, Nov 08 2001
Two more terms (148091 and 201107) from T. D. Noe, Feb 12 2003 and Mar 04 2003
397379 from T. D. Noe, Aug 18 2003
433781, 590041, 593689 from Henri Lifchitz submitted by Ray Chandler, Feb 11 2005
604711 from Henri Lifchitz communicated by Eric W. Weisstein, Nov 29 2005
931517, 1049897, 1285607 found by Henri Lifchitz circa Nov 01 2008 and submitted by Alexander Adamchuk, Nov 28 2008
1636007 from Henri Lifchitz March 2009, communicated by Eric W. Weisstein, Apr 24 2009
1803059 and 1968721 from Henri Lifchitz, November 2009, submitted by Alex Ratushnyak, Aug 08 2012
a(49)=2904353 from Henri Lifchitz, Jul 15 2014
a(50)=3244369 from Henri Lifchitz, Nov 04 2017


STATUS

approved



