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A227627 Numbers n such that F(5*n)/(5*F(n)) is prime, where F(k) is the k-th Fibonacci number. 1
2, 3, 5, 7, 13, 25, 29, 37, 47, 67, 457, 2309, 2383, 4133, 5023, 8059 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Except for n = 25, all other terms n are primes. Conjecture: this sequence is infinite. - Thomas Ordowski, Jul 18 2013

LINKS

Table of n, a(n) for n=1..16.

MATHEMATICA

Select[Range[1000], PrimeQ[Fibonacci[5*#]/Fibonacci[#]/5]&]

PROG

(PARI) is(n)=ispseudoprime(fibonacci(5*n)/fibonacci(n)/5) \\ Charles R Greathouse IV, Nov 25 2014

CROSSREFS

Cf. A227576, A088545, A000045, A001605.

Sequence in context: A076994 A327591 A124147 * A335116 A135372 A037021

Adjacent sequences:  A227624 A227625 A227626 * A227628 A227629 A227630

KEYWORD

nonn,more,hard

AUTHOR

Vaclav Kotesovec, Jul 18 2013

STATUS

approved

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Last modified May 11 00:43 EDT 2021. Contains 343784 sequences. (Running on oeis4.)