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 A001605 Indices of prime Fibonacci numbers. (Formerly M2309 N0911) 111
 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, 3340367 (list; graph; refs; listen; history; text; internal format)
 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 n-2 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(n-1) and F(n-1)*L(n+2) in some order, and F(n+2) > 1, L(n-1) > 1, F(n-1) > 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, Springer-Verlag, 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..51 J. Brillhart, P. L. Montgomery and R. D. Silverman, Tables of Fibonacci and Lucas factorizations, Math. Comp. 50 (1988), 251-260. 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, and 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) 417-427. 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 Alex Kontorovich and Jeff Lagarias, On Toric Orbits in the Affine Sieve, arXiv:1808.03235 [math.NT], 2018. Henri & Renaud Lifchitz, PRP Records. Tony D. Noe and Jonathan Vos Post, Primes in Fibonacci n-step and Lucas n-step 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) Lawrence Somer and Michal Křížek, On Primes in Lucas Sequences, Fibonacci Quart. 53 (2015), no. 1, 2-23. 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(n-S(m)) - abs(n-S(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. Column k=1 of A303215. Sequence in context: A081735 A227231 A107036 * A216570 A101762 A342752 Adjacent sequences:  A001602 A001603 A001604 * A001606 A001607 A001608 KEYWORD nonn,hard,nice AUTHOR 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 a(51)=3340367 from Henri Lifchitz, Apr 25 2018 STATUS approved

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Last modified June 24 05:58 EDT 2021. Contains 345416 sequences. (Running on oeis4.)