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A069237
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Composite n such that tau(n) divides phi(n), where tau(n) is the number of divisors of n and phi(n) the Euler totient function.
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2
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8, 9, 10, 15, 18, 21, 24, 26, 28, 30, 33, 34, 35, 39, 40, 45, 49, 51, 52, 55, 56, 57, 58, 63, 65, 69, 70, 72, 74, 76, 77, 78, 82, 84, 85, 87, 88, 90, 91, 93, 95, 98, 99, 102, 104, 105, 106, 108, 110, 111, 115, 117, 119, 120, 122, 123, 124, 125, 126, 128, 129, 130, 133
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OFFSET
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1,1
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COMMENTS
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LINKS
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MAPLE
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filter:= n -> not isprime(n) and numtheory:-phi(n) mod numtheory:-tau(n)=0:
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MATHEMATICA
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nn=200; Rest[Select[Complement[Range[nn], Prime[Range[PrimePi[nn]]]], Divisible[ EulerPhi[#], DivisorSigma[0, #]]&]] (* Harvey P. Dale, Mar 31 2011 *)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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