A141264 -id:A141264

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A103578

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

+10
2

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

(list; graph; refs; listen; history; text; internal format)

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.

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

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