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A074726 Numbers n such that sigma(F(n)) > 2*F(n) where F(n) is the n-th Fibonacci number. 1
12, 18, 24, 30, 36, 40, 42, 48, 54, 60, 72, 80, 84, 90, 96, 108, 120, 126, 132, 140, 144, 150, 156, 160, 162, 168, 180, 192, 198, 200, 204, 210, 216, 225, 228, 234, 240, 252, 264, 270, 276, 280, 288, 294, 300, 306, 312, 315, 320 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Conjecture: sigma(F(n)) > 2*F(n) if and only if F(n) is a Zumkeller number except for n = 12. Verified for n <= 371. - M. Farrokhi D. G., Aug 16 2020

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..216 (terms 1..156 from T. D. Noe)

Hisanori Mishima, Appendix 1. Factorization results links to internal pages

FORMULA

It seems that a(n) is asymptotic to c*n with 6 < c < 6.5.

MATHEMATICA

Select[ Range[256], DivisorSigma[1, Fibonacci[ #1]] > 2*Fibonacci[ #1] & ]

CROSSREFS

Cf. A000045, A063477, A074316.

Sequence in context: A341099 A175837 A136446 * A341475 A091013 A159886

Adjacent sequences:  A074723 A074724 A074725 * A074727 A074728 A074729

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Sep 04 2002

EXTENSIONS

Edited and extended by Robert G. Wilson v, Sep 06 2002

STATUS

approved

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Last modified April 12 17:48 EDT 2021. Contains 342929 sequences. (Running on oeis4.)