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A030627 Numbers with 9 divisors. 16
36, 100, 196, 225, 256, 441, 484, 676, 1089, 1156, 1225, 1444, 1521, 2116, 2601, 3025, 3249, 3364, 3844, 4225, 4761, 5476, 5929, 6561, 6724, 7225, 7396, 7569, 8281, 8649, 8836, 9025, 11236, 12321, 13225, 13924, 14161, 14884, 15129 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers of the form p^8 (8th row of A120458) or p^2*r^2 (A085986), where p and r are distinct primes. - R. J. Mathar, Mar 01 2010

LINKS

R. J. Mathar, Table of n, a(n) for n = 1..1000

FORMULA

A000005(a(n))=9. - Juri-Stepan Gerasimov, Oct 10 2009

MATHEMATICA

Select[Range[90000], DivisorSigma[0, #]==9&] (* Vladimir Joseph Stephan Orlovsky, May 05 2011 *)

PROG

(PARI) is(n)=numdiv(n)==9 \\ Charles R Greathouse IV, Jun 19 2016

CROSSREFS

Cf. A030515, A030516, A030626.

Sequence in context: A303606 A303661 A175391 * A177492 A077448 A085986

Adjacent sequences:  A030624 A030625 A030626 * A030628 A030629 A030630

KEYWORD

nonn

AUTHOR

Jeff Burch

STATUS

approved

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Last modified October 15 07:56 EDT 2019. Contains 328026 sequences. (Running on oeis4.)