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A112018
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Primes p of the form 4k+3 where sigma(phi(sigma(p)))= phi(sigma(phi(p))).
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OFFSET
| 1,1
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COMMENTS
| Between the first 480000000 primes, the equation (*): sigma(phi(sigma(x)))=phi(sigma(phi(x))) has 256 solutions q(i) and only four of them namely q(76),q(215),q(254) and q(256) are of the form 4k+3. Sequence A112017 gives composite solutions of the equation (*), which are of the form 4k+3.
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MATHEMATICA
| Do[If[Mod[Prime[m], 4]==3 && DivisorSigma[1, EulerPhi[Prime[m]+1 ==EulerPhi[DivisorSigma[1, Prime[m]-1]], Print[Prime[m]]], {m, 480000000}]
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CROSSREFS
| Cf. A112017.
Sequence in context: A147581 A171571 A205169 * A206751 A206062 A157770
Adjacent sequences: A112015 A112016 A112017 * A112019 A112020 A112021
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KEYWORD
| more,nonn
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AUTHOR
| Farideh Firoozbakht (mymontain(AT)yahoo.com), Sep 15 2005
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