A119239 Oddly superabundant numbers: odd n with sigma(n)/n > sigma(k)/k for all odd k < n.

1, 3, 9, 15, 45, 105, 315, 945, 1575, 2835, 3465, 10395, 17325, 31185, 45045, 135135, 225225, 405405, 675675, 2027025, 2297295, 3828825, 6891885, 11486475, 34459425, 43648605, 72747675, 130945815, 218243025, 654729075, 1003917915, 1527701175

Offset

1,2

Comments

Every oddly colossally abundant number (A110464) is in this sequence.

Links

T. D. Noe, Table of n, a(n) for n = 1..1000

Richard Laatsch, Measuring the abundancy of integers, Mathematics Magazine 59 (2) (1986) 84-92.

Walter Nissen, Abundancy : Some Resources

Mathematica

rec=0; lst={}; Do[abun=DivisorSigma[1, n]/n; If[abun>rec, rec=abun; AppendTo[lst, n]], {n, 1, 10^6, 2}]; lst

Prog

(PARI) r=0; forstep(n=1, 1e6, 2, t=sigma(n)/n; if(t>r, r=t; print1(n", "))) \\ Charles R Greathouse IV, Nov 27 2013

Crossrefs

Cf. A004394 (superabundant numbers), A005231 (odd abundant numbers), A053624 (highly composite odd numbers).

Sequence in context: A355771 A053624 A348198 * A140864 A171929 A188597

Adjacent sequences: A119236 A119237 A119238 * A119240 A119241 A119242

Keyword

nonn

Author

T. D. Noe, May 09 2006

Extensions

Definition clarified by Jonathan Sondow, Dec 08 2011

Status

approved