A103578 Number of divisors of m^2, where m is the smallest number with at least n divisors.

1, 3, 5, 9, 15, 15, 21, 21, 25, 27, 45, 45, 63, 63, 63, 63, 75, 75, 81, 81, 105, 105, 105, 105, 135, 135, 135, 135, 135, 135, 189, 189, 225, 225, 225, 225, 243, 243, 243, 243, 315, 315, 315, 315, 315, 315, 315, 315, 405, 405, 405, 405, 405, 405, 405, 405, 405

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

a(n) = A000005((A061799(n))^2). - R. J. Mathar, Sep 01 2008

Example

a(8) = 21 because smallest number with 8 divisors is 24, 24^2 = 576 and 576 has 21 divisors.

Mathematica

a = {}; i = 1; For[n = 1, n < 60, n++, While[DivisorSigma[0, i] < n, i++ ]; AppendTo[a, DivisorSigma[0, i^2]]]; a (* Stefan Steinerberger, Aug 31 2008 *)

Crossrefs

Cf. A000005, A061799, A141264.

Sequence in context: A071155 A120695 A355898 * A116649 A129771 A209837

Adjacent sequences: A103575 A103576 A103577 * A103579 A103580 A103581

Keyword

nonn

Author

Stefan Steinerberger, Aug 31 2008

Extensions

Edited by R. J. Mathar, Sep 01 2008, Dec 15 2008

Extended beyond a(8) by R. J. Mathar, Aug 31 2008

Status

approved