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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
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
Sequence in context: A270779 A350176 A248796 * A064080 A184875 A112986
KEYWORD
nonn,more
AUTHOR
Jaroslav Krizek, Nov 21 2014
STATUS
approved

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