A141645 Numbers n such that sigma(n)/n = 9/2.

8910720, 17428320, 8583644160, 57629644800, 206166804480, 1416963251404800, 15338300494970880, 6275163455171297280, 200286975596707184640, 215594611071909888000, 5997579964837140234240, 39887491844324122951680

Offset: 1

Author

Yasutoshi Kohmoto, May 10 2008

Keywords

• nonn

Comments

200286975596707184640 belongs to this sequence. - Gerard P. Michon, May 10 2009

81703797123392614369698250752 is in this sequence. - Gerard P. Michon, May 11 2009

Links

• G. P. Michon, Table of n, a(n) for n = 1..27
• G. P. Michon, Multiperfect and hemiperfect integers [From _Gerard P. Michon_, Jun 04 2009]
• Walter Nissen, Abundancy : Some Resources

Crossrefs

Cf. A055153, A141643, A159271, A160678.

Cf. A159907 = (half-integer abundancy). - Gerard P. Michon, May 10 2009

Programs

PARI

is(n)=sigma(n,-1)==9/2 \\ Charles R Greathouse IV, Mar 09 2014

Extensions

Definition rewritten by M. F. Hasler, May 10 2008

Is it certain that there are no other terms below the highest value shown? - N. J. A. Sloane, Sep 07 2008

a(1) corrected and a(3) confirmed by Ray Chandler, Sep 18 2008

Missing term a(2)=17428320 communicated by Walter Nissen, Apr 17 2009. There are no further terms through 2^34.

Missing term a(4) inserted and a(6) and a(8) added by Grzegorz Lach (137.036(AT)gmail.com), Apr 18 2009. a(4) was also sent by Avinoam Kalma (a.kalma(AT)gmail.com), Apr 20 2009.

a(7) = 15338300494970880 added by Gerard P. Michon, May 10 2009.

a(10)=215594611071909888000 [and above] from Michel Marcus, added by Gerard P. Michon, Jun 04 2009