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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
OFFSET
1,1
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 A348343 A237862
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Feb 05 2002
EXTENSIONS
More terms from Michel Marcus, Nov 22 2013
STATUS
approved