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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

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Last modified February 24 20:33 EST 2020. Contains 332210 sequences. (Running on oeis4.)