|
| |
|
|
A023197
|
|
Numbers k such that sigma(k) >= 3*k.
|
|
15
|
|
|
|
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
Richard Laatsch, Measuring the Abundancy of Integers, Mathematics Magazine, Vol. 59, No. 2 (1986), pp. 84-92, alternative link.
|
|
|
FORMULA
|
A001221(a(n)) >= 3 (Laatsch, 1986). - Amiram Eldar, Nov 07 2020
|
|
|
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. A000203, A001221, A119240.
See A033880 for definition of k-abundancy.
Sequence in context: A232461 A090782 A337386 * A204828 A204830 A279088
Adjacent sequences: A023194 A023195 A023196 * A023198 A023199 A023200
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
David W. Wilson
|
|
|
STATUS
|
approved
|
| |
|
|
