The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A144922 Numbers n such that n*sigma_2(n)/sigma_1(n) is an integer 1
 1, 4, 6, 9, 12, 16, 18, 20, 24, 25, 28, 36, 44, 45, 48, 49, 50, 54, 60, 64, 72, 81, 90, 92, 96, 100, 108, 112, 117, 121, 132, 140, 144, 150, 153, 162, 168, 169, 180, 192, 196, 198, 200, 204, 216, 225, 228, 234, 240, 242, 252, 256, 270, 288, 289, 294, 300 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS n*A001157(n)/A000203(n) is an integer. This sequence is connected closely with Ore divisor numbers (A001599) and RMS numbers (A140480). LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 MATHEMATICA Select[Range[300], IntegerQ[(#*DivisorSigma[2, #])/DivisorSigma[1, #]]&] (* Harvey P. Dale, Oct 28 2018 *) CROSSREFS Cf. A000203, A001157, A001599, A140480 Sequence in context: A274135 A163656 A100915 * A298864 A310667 A317538 Adjacent sequences:  A144919 A144920 A144921 * A144923 A144924 A144925 KEYWORD easy,nonn AUTHOR Ctibor O. Zizka, Sep 25 2008 EXTENSIONS More terms from Harvey P. Dale, Oct 28 2018 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
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified November 29 18:41 EST 2021. Contains 349416 sequences. (Running on oeis4.)