A030638 Numbers with 20 divisors.

240, 336, 432, 528, 560, 624, 648, 810, 816, 880, 912, 1040, 1104, 1134, 1232, 1360, 1392, 1456, 1488, 1520, 1536, 1776, 1782, 1840, 1904, 1968, 2000, 2064, 2106, 2128, 2256, 2288, 2320, 2480, 2544, 2560, 2576, 2754, 2832, 2835, 2928

Offset

1,1

Comments

Numbers of the form p^19, p*q^9 (A179692), p*q*r^4 (A179644) or p^3*q^4 (A179666), where p, q and r are distinct primes. - R. J. Mathar, Mar 01 2010

Links

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

Mathematica

Select[Range[20000], DivisorSigma[0, #]==20&] (* Vladimir Joseph Stephan Orlovsky, May 05 2011 *)

Prog

(PARI) is(n)=numdiv(n)==20 \\ Charles R Greathouse IV, Jun 19 2016

Crossrefs

Cf. A030636, A030637, A137484.

Sequence in context: A067373 A291921 A257413 * A179644 A099833 A272950

Adjacent sequences: A030635 A030636 A030637 * A030639 A030640 A030641

Keyword

nonn

Author

Jeff Burch

Status

approved