A080651 - OEIS

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A080651

Numbers n such that n and Fibonacci(n) have the same number of divisors.

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

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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: A343217 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