The OEIS is supported by the many generous donors to the OEIS Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A112018 Primes p of the form 4k+3 where sigma(phi(sigma(p)))= phi(sigma(phi(p))). 0
 114190259, 6364631939, 10296994891, 10429820759 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 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. LINKS 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}] CROSSREFS Cf. A112017. Sequence in context: A171571 A208491 A205169 * A216010 A206751 A206062 Adjacent sequences:  A112015 A112016 A112017 * A112019 A112020 A112021 KEYWORD more,nonn AUTHOR Farideh Firoozbakht, Sep 15 2005 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 17 20:06 EST 2022. Contains 350410 sequences. (Running on oeis4.)