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A134639 Conjectured number of numbers k such that sigma(k)/k = n. 2
6, 36, 65, 245, 516 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

COMMENTS

These numbers come from Guy and Flammenkamp. Sequences A000396, A005820, A027687, A046060 and A046061 give the k for which the abundancy sigma(k)/k is 2, 3, 4, 5 and 6, respectively. Sequence A054030 gives the abundancy of each multiperfect number A007691.

REFERENCES

R. K. Guy, Unsolved Problems in Number Theory, 3rd Ed., New York, Springer-Verlag, 2004, Section B2.

LINKS

Table of n, a(n) for n=3..7.

Achim Flammenkamp, The Multiply Perfect Numbers Page

CROSSREFS

Sequence in context: A207590 A226119 A036148 * A069497 A139249 A070150

Adjacent sequences:  A134636 A134637 A134638 * A134640 A134641 A134642

KEYWORD

nonn

AUTHOR

T. D. Noe, Nov 05 2007

STATUS

approved

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Last modified March 22 22:17 EDT 2017. Contains 283901 sequences.