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

 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! The asymptotic density of this sequence is in the interval (0.491096, 0.491156) (based on the known bounds on the densities of A005101 and A005231; see A302991 and A322287). - Amiram Eldar, Mar 11 2024 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, A302991, A322287. 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.

Last modified June 22 12:42 EDT 2024. Contains 373571 sequences. (Running on oeis4.)