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A067708 Numbers n such that phi(sigma(n)) = 5*phi(n). 0
336, 1008, 1680, 4368, 5040, 12432, 13104, 21840, 24528, 37296, 52752, 57792, 62160, 64848, 65520, 73584, 93072, 105168, 122640, 128520, 133392, 141456, 153552, 158256, 161616, 167700, 173376, 181776, 186480, 194544, 205968, 222096, 226128, 246288, 254352 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..35.

MATHEMATICA

Select[Range[260000], EulerPhi[DivisorSigma[1, #]]==5*EulerPhi[#]&] (* Harvey P. Dale, Jul 11 2018 *)

PROG

(PARI) isok(n) = eulerphi(sigma(n)) == 5*eulerphi(n); \\ Michel Marcus, Nov 22 2013

CROSSREFS

Cf. A067706.

Sequence in context: A064259 A181256 A006909 * A059467 A237862 A268807

Adjacent sequences:  A067705 A067706 A067707 * A067709 A067710 A067711

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Feb 05 2002

EXTENSIONS

More terms from Michel Marcus, Nov 22 2013

STATUS

approved

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Last modified October 15 15:14 EDT 2019. Contains 328030 sequences. (Running on oeis4.)