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Search: id:A163665
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| A163665 |
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Numbers n such that n=prime(phi(sigma(pi(n)))). |
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+0
2
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| 2, 3, 19, 37, 719, 1511, 5443, 69709, 386093, 1907819, 10777931, 17819101, 18653749, 56125547, 60163267, 98911811, 272887613, 567611663, 989060309, 2444540149
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OFFSET
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1,1
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COMMENT
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It is obvious that all terms are primes. There is no further term up to 5*10^9.
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MATHEMATICA
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Do[If[n=Prime[m]; m==EulerPhi[DivisorSigma[1, PrimePi[n]]], Print[n]], {m, 235000000}]
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CROSSREFS
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Cf. A000010, A000040, A000720, A000203, A163666.
Sequence in context: A142955 A088790 A135958 this_sequence A051079 A051089 A157042
Adjacent sequences: A163662 A163663 A163664 this_sequence A163666 A163667 A163668
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KEYWORD
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more,nonn
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AUTHOR
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Farideh Firoozbakht (mymontain(AT)yahoo.com), Aug 04 2009
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