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Search: id:A070171
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| A070171 |
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Numbers n such that sigma(phi(n))=n-phi(n). |
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+0
2
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OFFSET
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1,1
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COMMENT
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No other term < 20000000. All terms 2 < a(n) < 20000000 are divisible by 6.
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MATHEMATICA
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Do[s=DivisorSigma[1, EulerPhi[n]]-(n-EulerPhi[n]); If[Equal[s, 0], Print[n]], {n, 1, 2000000}]
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PROGRAM
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(PARI) for(n=2, 2000000, if(sigma(eulerphi(n))==n-eulerphi(n), print1(n, ", ")))
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CROSSREFS
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Cf. A070170.
Sequence in context: A064057 A091940 A068605 this_sequence A036800 A157052 A052633
Adjacent sequences: A070168 A070169 A070170 this_sequence A070172 A070173 A070174
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KEYWORD
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easy,more,nonn
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AUTHOR
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Benoit Cloitre and Elemer Labos, May 06 2002
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