A146566 Numbers k such that k*sigma_0(k) is divisible by (k - sigma_0(k)).

3, 4, 6, 8, 12, 18, 24, 36, 40, 60, 84, 156, 180, 600

Offset: 1

Author

Ctibor O. Zizka, Nov 01 2008

Keywords

• nonn
• more

Comments

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

No other term multiple of 12 below 10^9. - M. F. Hasler, Apr 16 2022

Crossrefs

Cf. A000005, A049820, A352483.

Programs

Mathematica

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

PARI

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

PARI

is_A146566(n,d=numdiv(n))={n*d%(n-d)==0} \\ M. F. Hasler, Apr 16 2022

Formula

A352483(a(n)) = 1. - Bernard Schott, Mar 23 2022

Extensions

Corrected and extended by Michel Marcus, Jun 02 2013