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Search: id:A163666
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| A163666 |
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Numbers n such that n=prime(sigma(phi(pi(n)))). |
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2
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| 2, 5, 47, 107, 1613, 5653, 21557, 230047, 821603, 8145173, 47073007, 68939141, 76040521, 196388147, 240595631, 433046543, 1085166671, 2269551127, 4670405591
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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==DivisorSigma[1, EulerPhi[PrimePi[n]]], Print[n]], {m, 235000000}]
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CROSSREFS
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Cf. A000010, A000040, A000720, A000203, A163665.
Sequence in context: A023273 A041729 A078665 this_sequence A093552 A112266 A060808
Adjacent sequences: A163663 A163664 A163665 this_sequence A163667 A163668 A163669
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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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