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A067708
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Numbers n such that phi(sigma(n)) = 5*phi(n).
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0
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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
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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Select[Range[260000], EulerPhi[DivisorSigma[1, #]]==5*EulerPhi[#]&] (* Harvey P. Dale, Jul 11 2018 *)
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PROG
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(PARI) isok(n) = eulerphi(sigma(n)) == 5*eulerphi(n); \\ Michel Marcus, Nov 22 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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