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A060383 a(1) = a(2) = 1; for n >2, a(n) = smallest prime factor of n-th Fibonacci number. 4
1, 1, 2, 3, 5, 2, 13, 3, 2, 5, 89, 2, 233, 13, 2, 3, 1597, 2, 37, 3, 2, 89, 28657, 2, 5, 233, 2, 3, 514229, 2, 557, 3, 2, 1597, 5, 2, 73, 37, 2, 3, 2789, 2, 433494437, 3, 2, 139, 2971215073, 2, 13, 5, 2, 3, 953, 2, 5, 3, 2, 59, 353, 2, 4513, 557, 2, 3, 5, 2, 269, 3, 2, 5 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..1408 (terms 1..1000 from Alois P. Heinz, derived from Kelly's data)

Blair Kelly, Fibonacci and Lucas Factorizations

FORMULA

a(n) = A020639(A000045(n)). - Michel Marcus, Nov 15 2014

EXAMPLE

For n=82: F(82) = 2789*59369*370248451, so a(82)=2789.

MATHEMATICA

f[n_] := (FactorInteger@ Fibonacci@ n)[[1, 1]]; Array[f, 70] (* Robert G. Wilson v, Jul 07 2007 *)

PROG

(PARI) a(n) = if ((f=fibonacci(n))==1, 1, factor(f)[1, 1]); \\ Michel Marcus, Nov 15 2014

(MAGMA) [1, 1] cat [Minimum(PrimeDivisors(Fibonacci(n))): n in [3..70]]; // Vincenzo Librandi, Dec 25 2016

CROSSREFS

Cf. A000045, A022307, A001605, A060319, A060320, A051694.

Sequence in context: A137458 A079369 A102867 * A139044 A060442 A060385

Adjacent sequences:  A060380 A060381 A060382 * A060384 A060385 A060386

KEYWORD

nonn

AUTHOR

Labos Elemer, Apr 03 2001

EXTENSIONS

Better definition from Omar E. Pol, Apr 25 2008

STATUS

approved

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Last modified February 20 08:00 EST 2020. Contains 332069 sequences. (Running on oeis4.)