OFFSET
1,1
COMMENTS
Subsequence of A066881. - R. J. Mathar, Sep 30 2008
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..500
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