A015834 - OEIS

A015834

Numbers k such that phi(k) | sigma(k + 1).

1, 2, 4, 5, 6, 9, 10, 13, 14, 20, 21, 30, 32, 34, 43, 45, 54, 55, 65, 68, 70, 104, 109, 114, 129, 132, 140, 151, 153, 160, 176, 183, 203, 234, 245, 252, 279, 314, 340, 370, 407, 434, 441, 539, 550, 580, 589, 620, 635, 644, 741, 765, 798, 806, 845, 860, 883

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OFFSET

1,2

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..1000

MATHEMATICA

Select[Range[3000], Divisible[DivisorSigma[1, 1 + #], EulerPhi[#]] &] (* David Nacin, Mar 03 2012 *)

PROG

(PARI) is(n)=!(sigma(n+1)%eulerphi(n)) \\ Charles R Greathouse IV, Sep 25 2012

CROSSREFS

Sequence in context: A120629 A169694 A285163 * A252041 A231587 A050011

Adjacent sequences: A015831 A015832 A015833 * A015835 A015836 A015837