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A064593 Nonunitary triply perfect numbers: the sum of the nonunitary divisors of n is 3n; i.e., sigma(n) - usigma(n) = 3n. 5
186076800, 3456573120, 18924364800, 325377803520, 2666567816640, 8538872307840, 11169839116800 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

There are no others up to 1.6*10^13, but there are at least 20 larger ones, between 87916260096000 and 19424258892617980729341453189120.

Ligh & Wall found a(1), a(4) and a(5). - Amiram Eldar, Sep 27 2018

LINKS

Table of n, a(n) for n=1..7.

Steve Ligh and Charles R. Wall, Functions of Nonunitary Divisors, Fibonacci Quarterly, Vol. 25 (1987), pp. 333-338.

CROSSREFS

Cf. A048146, A064591, A064592, A064594, A064595, A064596.

Sequence in context: A253941 A230222 A061440 * A084304 A228377 A178565

Adjacent sequences:  A064590 A064591 A064592 * A064594 A064595 A064596

KEYWORD

nonn,hard

AUTHOR

Dean Hickerson, Sep 25 2001

STATUS

approved

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Last modified October 17 14:22 EDT 2018. Contains 316281 sequences. (Running on oeis4.)