login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A039725 Even abundant numbers divided by 2.
(Formerly N1690)
3
6, 9, 10, 12, 15, 18, 20, 21, 24, 27, 28, 30, 33, 35, 36, 39, 40, 42, 44, 45, 48, 50, 51, 52, 54, 56, 57, 60, 63, 66, 69, 70, 72, 75, 78, 80, 81, 84, 87, 88, 90, 93, 96, 98, 99, 100, 102, 104, 105, 108, 110, 111, 112, 114, 117, 120, 123, 126, 129, 130, 132, 135, 136 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

While the first even abundant number is 12 = 2^2*3, the first odd abundant is 945 = 3^3*5*7, the 232nd abundant number!

REFERENCES

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

LINKS

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

FORMULA

a(n) = A173490(n) / 2.

EXAMPLE

The first even abundant number is 12, so 12/2 = 6 is the first element in this sequence.

MATHEMATICA

Select[Range[2, 300, 2], DivisorSigma[1, #]>2*#&]/2 (* Harvey P. Dale, Mar 22 2020 *)

CROSSREFS

Cf. A005101, A005231, A173490.

Sequence in context: A177201 A090466 A090428 * A262362 A125494 A177029

Adjacent sequences: A039722 A039723 A039724 * A039726 A039727 A039728

KEYWORD

easy,nonn

AUTHOR

N. J. A. Sloane. This was included in the 1973 "Handbook", but was then dropped from the database. Resubmitted by James A. Sellers. Entry revised by N. J. A. Sloane, Jun 12 2012

EXTENSIONS

Corrected and edited by Daniel Forgues, Nov 22 2010

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 5 19:04 EST 2022. Contains 358588 sequences. (Running on oeis4.)