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A146566 Numbers n such that n*sigma_0(n)/(n-sigma_0(n))= c, c an integer. 2
3, 4, 6, 8, 12, 18, 24, 36, 40, 60, 84, 156, 180, 600 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A000027(n)*A000005(n)/(A000027(n)-A000005(n))=c, c an integer.

No other term < 10000000. - Michel Marcus, Jun 02 2013

LINKS

Table of n, a(n) for n=1..14.

MATHEMATICA

nsiQ[n_]:=Module[{s=DivisorSigma[0, n]}, IntegerQ[(n*s)/(n-s)]]; Select[ Range[3, 600], nsiQ] (* Harvey P. Dale, Dec 05 2019 *)

PROG

(PARI) isok(n) = {nd = numdiv(n); type(n*nd/(n-nd)) == "t_INT"}  \\ Michel Marcus, Jun 02 2013

CROSSREFS

Cf. A000027, A000005

Sequence in context: A163978 A145751 A277099 * A204658 A139041 A244607

Adjacent sequences:  A146563 A146564 A146565 * A146567 A146568 A146569

KEYWORD

easy,nonn

AUTHOR

Ctibor O. Zizka, Nov 01 2008

EXTENSIONS

Corrected and extended by Michel Marcus, Jun 02 2013

STATUS

approved

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Last modified January 22 03:32 EST 2021. Contains 340360 sequences. (Running on oeis4.)