A064593 Nonunitary triply perfect numbers: the sum of the nonunitary divisors of n is 3n; i.e., sigma(n) - usigma(n) = 3n.

186076800, 3456573120, 18924364800, 325377803520, 2666567816640, 8538872307840, 11169839116800

Offset: 1

Author

Dean Hickerson, Sep 25 2001

Keywords

• nonn
• hard

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

• 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.