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A080651 Numbers n such that n and Fibonacci(n) have the same number of divisors. 2
1, 3, 5, 6, 7, 8, 10, 11, 13, 14, 17, 22, 23, 26, 29, 34, 43, 47, 83, 94, 131, 137, 359, 431, 433, 449, 509, 569, 571, 2971, 4723, 5387, 9311, 9677, 14431 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Except for A001605(2) = 4, all terms of A001605 are terms of this sequence. - Chai Wah Wu, Dec 30 2019

LINKS

Table of n, a(n) for n=1..35.

Blair Kelly, Fibonacci and Lucas Factorizations.

FORMULA

a(n) = A001605(n-8) for n >= 21 (conjectured). - Chai Wah Wu, Dec 30 2019

MATHEMATICA

Select[Range[2*10^2], DivisorSigma[0, Fibonacci[ # ]] == DivisorSigma[0, # ] &]

PROG

(PARI) isok(n) = numdiv(n) == numdiv(fibonacci(n)); \\ Michel Marcus, Feb 25 2016

CROSSREFS

Cf. A001605, A063375.

Sequence in context: A181744 A160685 A080218 * A047330 A093511 A039041

Adjacent sequences:  A080648 A080649 A080650 * A080652 A080653 A080654

KEYWORD

nonn,more

AUTHOR

Joseph L. Pe, Feb 28 2003

EXTENSIONS

More terms from Ryan Propper, May 31 2006

a(30)-a(34) from Chai Wah Wu, Dec 30 2019

a(35) from Chai Wah Wu, Dec 31 2019

STATUS

approved

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Last modified September 22 11:22 EDT 2020. Contains 337289 sequences. (Running on oeis4.)