The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A247164 Primes p such that Product_{d|(p-2)} phi(d) = Product_{d|(p-1)} phi(d) where phi(x) = Euler totient function (A000010). 2
 3, 5, 7, 17, 257, 65537, 991172807 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes p such that A029940(p-2) = A029940(p-1). First 5 known terms of Fermat primes (A019434) are terms of this sequence. Subsequence of A248796. Supersequence of A247203. LINKS Table of n, a(n) for n=1..7. FORMULA A029940(a(n)) = a(n)-1. EXAMPLE Prime 17 is in the sequence because A029940(15) = A029940(16) = 64. PROG (Magma) [n: n in [3..100000] | IsPrime(n) and (&*[EulerPhi(d): d in Divisors(n-2)]) eq (&*[EulerPhi(d): d in Divisors(n-1)])] CROSSREFS Cf. A000010, A019434, A029940, A248795, A248796. Sequence in context: A270779 A350176 A248796 * A064080 A184875 A112986 Adjacent sequences: A247161 A247162 A247163 * A247165 A247166 A247167 KEYWORD nonn,more AUTHOR Jaroslav Krizek, Nov 21 2014 STATUS approved

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

Last modified July 13 04:46 EDT 2024. Contains 374267 sequences. (Running on oeis4.)