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A144922 Numbers n such that n*sigma_2(n)/sigma_1(n) is an integer 1


%S 1,4,6,9,12,16,18,20,24,25,28,36,44,45,48,49,50,54,60,64,72,81,90,92,

%T 96,100,108,112,117,121,132,140,144,150,153,162,168,169,180,192,196,

%U 198,200,204,216,225,228,234,240,242,252,256,270,288,289,294,300

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

%C n*A001157(n)/A000203(n) is an integer. This sequence is connected closely with Ore divisor numbers (A001599) and RMS numbers (A140480).

%H Harvey P. Dale, <a href="/A144922/b144922.txt">Table of n, a(n) for n = 1..1000</a>

%t Select[Range[300],IntegerQ[(#*DivisorSigma[2,#])/DivisorSigma[1,#]]&] (* _Harvey P. Dale_, Oct 28 2018 *)

%Y Cf. A000203, A001157, A001599, A140480

%K easy,nonn

%O 1,2

%A _Ctibor O. Zizka_, Sep 25 2008

%E More terms from _Harvey P. Dale_, Oct 28 2018

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Last modified January 23 03:15 EST 2022. Contains 350504 sequences. (Running on oeis4.)