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A114842 Indices of Fibonacci numbers with 2 distinct prime factors. 3
8, 9, 10, 12, 14, 19, 22, 25, 26, 31, 34, 41, 53, 59, 61, 71, 73, 79, 89, 94, 101, 107, 109, 113, 121, 127, 151, 167, 173, 191, 193, 199, 227, 251, 271, 277, 293, 331, 353, 397, 401, 467, 587, 599, 601, 613, 631, 653, 743, 991, 1091, 1223, 1373 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A072381 is subsequence, since the only square Fibonacci numbers are 1 and 144 which are not squares of primes. - Charles R Greathouse IV, Sep 24 2012

LINKS

Table of n, a(n) for n=1..53.

Yann Bugeaud, Florian Luca, Maurice Mignotte, and Samir Siksek, On Fibonacci numbers with few prime divisors, Proc. Japan Acad. Ser. A Math. Sci., Volume 81, Number 2 (2005), 17-20.

EXAMPLE

a(1) = 8 because 8th Fibonacci number consists of 2 distinct prime factors (i.e. 21 = 3*7).

25 is in the sequence because Fibonacci(25) = 75025 = 5^2 * 3001 consists of 2 distinct prime factors.

PROG

(PARI) n=1; while(n<355, if(omega(fibonacci(n))==2, print1(n, ", ")); n++)

CROSSREFS

Cf. A114823-A114826, A114836-A114841.

Column k=2 of A303217.

Sequence in context: A054011 A280946 A209724 * A169928 A067683 A164276

Adjacent sequences:  A114839 A114840 A114841 * A114843 A114844 A114845

KEYWORD

hard,more,nonn

AUTHOR

Shyam Sunder Gupta, Feb 19 2006

EXTENSIONS

a(40)-a(50) from Donovan Johnson, Sep 27 2008

a(51)-a(52) from Max Alekseyev, Aug 18 2013

a(53) from Amiram Eldar, Oct 14 2019

STATUS

approved

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Last modified June 1 13:11 EDT 2020. Contains 334762 sequences. (Running on oeis4.)