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Search: id:A104905
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| A104905 |
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Numbers n such that d(n)*phi(n)=sigma(n), where d(n) is number of positive divisors of n. |
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+0
4
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OFFSET
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1,2
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COMMENT
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No further term up to 530000000.
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EXAMPLE
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42 is in the sequence because d(42)=8; phi(42)=12; sigma(42)=96 & 8*12=96.
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MATHEMATICA
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Do[If[DivisorSigma[0, n]*EulerPhi[n] == DivisorSigma[1, n], Print[n]], {n, 530000000}]
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CROSSREFS
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Cf. A063903, A104904, A104906.
Sequence in context: A005701 A050297 A117662 this_sequence A055650 A000550 A124650
Adjacent sequences: A104902 A104903 A104904 this_sequence A104906 A104907 A104908
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KEYWORD
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more,nonn
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AUTHOR
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Farideh Firoozbakht (f.firoozbakht(AT)math.ui.ac.ir), Apr 13 2005
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