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A067383 Numbers n such that sigma(phi(n))/sigma(n) = 3. 7
181, 899, 2501, 4687, 10991, 12989, 17653, 25199, 25853, 26549, 26657, 54473, 65941, 68381, 72007, 82777, 96197, 98903, 102719, 116449, 124013, 135907, 150121, 169153, 188917, 193553, 201173, 207461, 219559, 234301, 237961, 239279 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..1000

MATHEMATICA

For[ n=1, True, n++, If[ DivisorSigma[ 1, EulerPhi[ n ] ]/DivisorSigma[ 1, n ]==3, Print[ n ] ] ]

PROG

(PARI) is(n)=sigma(eulerphi(n=factor(n)))/sigma(n)==3 \\ Charles R Greathouse IV, Nov 27 2013

CROSSREFS

Cf. A033631, A066831, A067382, A067384, A067385, A197952.

Sequence in context: A154628 A142731 A229877 * A107255 A163442 A268520

Adjacent sequences:  A067380 A067381 A067382 * A067384 A067385 A067386

KEYWORD

nonn

AUTHOR

Dean Hickerson, Jan 20 2002

STATUS

approved

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Last modified May 29 14:18 EDT 2020. Contains 334700 sequences. (Running on oeis4.)