A030636 Numbers with 18 divisors.

180, 252, 288, 300, 396, 450, 468, 588, 612, 684, 700, 768, 800, 828, 882, 972, 980, 1044, 1100, 1116, 1280, 1300, 1332, 1452, 1476, 1548, 1568, 1575, 1692, 1700, 1792, 1900, 1908, 2028, 2124, 2156, 2178, 2196, 2205, 2300, 2412, 2420, 2450

Offset: 1

Author

Jeff Burch

Keywords

• nonn

Comments

Numbers of the form p^17, p*q^8 (A179668), p*q^2*r^2 (A179643) or p^2*q^5 (A179646), 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

Crossrefs

Cf. A030635 (17 divs), A030637 (19 divs).

Programs

Mathematica

Select[Range[2500],DivisorSigma[0,#]==18&]  (* Harvey P. Dale, Feb 01 2011 *)

PARI

is(n)=numdiv(n)==18 \\ Charles R Greathouse IV, Jun 19 2016

Extensions

882 inserted by N. J. A. Sloane, Mar 26 2007