login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A218407 Numbers n for which sigma(n)/n = k+2/5 with integer k. 4
30, 140, 2480, 6200, 40640, 297600, 997920, 64995840, 167751680, 1502582400, 42949345280, 183196016640, 687193456640, 1447428787200, 63870637017600, 326676430080000, 20797363851264000, 24871926476966400, 42981218625945600, 404918548479244800 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(12) > 10^11. - Donovan Johnson, Oct 31 2012

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

Note that there no terms here with abundancy 7/5 (k=1). - Michel Marcus, Jun 26 2013

LINKS

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

FORMULA

sigma(n)/n = k+2/5 with integer k.

CROSSREFS

Cf. A218406, A218408, A218427.

Sequence in context: A158462 A064495 A267904 * A229450 A124958 A126417

Adjacent sequences:  A218404 A218405 A218406 * A218408 A218409 A218410

KEYWORD

nonn

AUTHOR

Zdenek Cervenka, Oct 28 2012

EXTENSIONS

a(8)-a(11) from Donovan Johnson, Oct 31 2012

a(12)-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 November 14 10:04 EST 2019. Contains 329111 sequences. (Running on oeis4.)