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A067384
Numbers n such that sigma(phi(n))/sigma(n) = 4.
6
121679, 1043909, 2350171, 2918263, 3396103, 3566807, 3688067, 4019467, 4562827, 5963407, 7300697, 7485979, 7853933, 8103301, 8364151, 9237779, 9514213, 9638527, 10531123, 11094619, 11384447, 12721937, 13576267
OFFSET
1,1
COMMENTS
Subsequence of A066881. - R. J. Mathar, Sep 30 2008
LINKS
MATHEMATICA
For[ n=1, True, n++, If[ DivisorSigma[ 1, EulerPhi[ n ] ]/DivisorSigma[ 1, n ]==4, Print[ n ] ] ]
PROG
(PARI) is(n)=sigma(phi(n=factor(n)))/sigma(n)==4 \\ Charles R Greathouse IV, Nov 27 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Dean Hickerson, Jan 20 2002
STATUS
approved