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A015834 Numbers k such that phi(k) | sigma(k + 1). 7
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
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
KEYWORD
nonn
AUTHOR
EXTENSIONS
a(1) = 1 inserted by Ivan Neretin, Feb 05 2017
STATUS
approved

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Last modified May 29 14:11 EDT 2024. Contains 372952 sequences. (Running on oeis4.)