login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A218427 Numbers n for which sigma(n)/n = k+4/5 with integer k. 4
10, 60, 1170, 114660, 72602880, 668304000, 714954240, 1307124000, 1381161600, 2701389600, 8052817920, 10181689600, 643773312000, 1330464844800, 2015156183040, 3522876144480, 15462510336000, 23885971200000, 702577007193600, 908714417345280 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(13) > 10^11. - Donovan Johnson, Oct 31 2012

a(14) > 10^12. - Giovanni Resta, Nov 04 2012

LINKS

Table of n, a(n) for n=1..20.

M. Drennen, T. Gunter, P. Johnson and J. Ward, The Loneliest Number

Jeffrey Ward, Does Ten Have a Friend?, arXiv:0806.1001

FORMULA

sigma(n)/n = k+4/5 with integer k.

CROSSREFS

Cf. A218406, A218407, A218408.

Sequence in context: A219368 A052664 A090373 * A041184 A089034 A261938

Adjacent sequences:  A218424 A218425 A218426 * A218428 A218429 A218430

KEYWORD

nonn

AUTHOR

Zdenek Cervenka, Oct 28 2012

EXTENSIONS

a(5)-a(12) from Donovan Johnson, Oct 31 2012

a(13) from Giovanni Resta, Nov 04 2012

More terms from Michel Marcus, Jun 26 2013

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 7 16:01 EDT 2020. Contains 335496 sequences. (Running on oeis4.)