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A309553 Imperfect numbers of the form 2^(2^k-1)*F_1*F_2*...*F_(k-1), where F is a Fermat number. 0
40, 10880, 715816960, 3074457344902430720 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers of this form are imperfect only for k = 2, 3, 4, 5.

LINKS

Table of n, a(n) for n=1..4.

László Tóth, A survey of the alternating sum-of-divisors function, arXiv:1111.4842 [math.NT], 2011-2014, end of section 8.

László Tóth, A survey of the alternating sum-of-divisors function, Acta Universitatis Sapientiae, Mathematica, Vol. 5, No. 1 (2013), pp. 93-107.

EXAMPLE

For k=2, 2^3*F_1 = 8*5 = 40, so 40 is in the sequence.

CROSSREFS

Cf. A000215, A127724.

Sequence in context: A183766 A184892 A119525 * A123381 A210347 A221391

Adjacent sequences:  A309550 A309551 A309552 * A309554 A309555 A309556

KEYWORD

nonn,fini,full

AUTHOR

Jud McCranie, Aug 07 2019

STATUS

approved

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Last modified October 25 06:19 EDT 2021. Contains 348239 sequences. (Running on oeis4.)