This site is supported by donations to The OEIS Foundation.

The OEIS is looking to hire part-time people to help edit core sequences, upload scanned documents, process citations, fix broken links, etc. - Neil Sloane, njasloane@gmail.com

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A030638 Numbers with 20 divisors. 17
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers of the form p^19, p*q^9, 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: A031173 A067373 A257413 * A179644 A099833 A272950 Adjacent sequences:  A030635 A030636 A030637 * A030639 A030640 A030641 KEYWORD nonn AUTHOR STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.