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A141645 Numbers n such that sigma(n)/n = 9/2. 9
8910720, 17428320, 8583644160, 57629644800, 206166804480, 1416963251404800, 15338300494970880, 6275163455171297280, 200286975596707184640, 215594611071909888000, 5997579964837140234240, 39887491844324122951680 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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

PROG

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

CROSSREFS

Cf. A055153, A141643, A159271, A160678.

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

Sequence in context: A233476 A078143 A216003 * A217655 A151933 A233492

Adjacent sequences:  A141642 A141643 A141644 * A141646 A141647 A141648

KEYWORD

nonn

AUTHOR

Yasutoshi Kohmoto, May 10 2008

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

STATUS

approved

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Last modified March 28 22:27 EDT 2017. Contains 284249 sequences.