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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A023197 Numbers n such that sigma(n) >= 3n. 14
120, 180, 240, 360, 420, 480, 504, 540, 600, 660, 672, 720, 780, 840, 900, 960, 1008, 1080, 1200, 1260, 1320, 1344, 1440, 1512, 1560, 1584, 1620, 1680, 1800, 1848, 1872, 1890, 1920, 1980, 2016, 2040, 2100, 2160, 2184, 2280, 2340, 2352, 2376, 2400, 2520 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Sometimes called 3-abundant numbers (but compare the comments in A033880). The first odd number is A119240(3) = 1018976683725. - T. D. Noe, Mar 31 2011

REFERENCES

Melvyn B. Nathanson, Elementary Methods in Number Theory, Springer, 2000, p 260.

LINKS

T. D. Noe, Table of n, a(n) for n = 1..10000

MAPLE

select(t -> numtheory:-sigma(t) >= 3*t, [$1..10000]); # Robert Israel, Dec 28 2014

MATHEMATICA

Select[Range[10000], DivisorSigma[1, #] >= 3*#&] (* Vladimir Joseph Stephan Orlovsky, Apr 21 2010 *)

CROSSREFS

Cf. A119240. See A033880 for definition of k-abundancy.

Sequence in context: A189975 A232461 A090782 * A204828 A204830 A279088

Adjacent sequences:  A023194 A023195 A023196 * A023198 A023199 A023200

KEYWORD

nonn

AUTHOR

David W. Wilson

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 June 19 23:01 EDT 2019. Contains 324222 sequences. (Running on oeis4.)