A144922 Numbers n such that n*sigma_2(n)/sigma_1(n) is an integer

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

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: A163656 A134678 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