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A066670
Primes arising in A066669: the only odd prime divisor of phi(A066669(n)).
4
3, 3, 5, 3, 3, 3, 3, 5, 11, 5, 3, 3, 7, 5, 3, 3, 3, 5, 3, 5, 3, 11, 23, 5, 3, 13, 5, 3, 7, 29, 3, 5, 11, 3, 3, 5, 3, 5, 41, 3, 7, 5, 11, 3, 11, 23, 3, 5, 3, 3, 13, 53, 5, 3, 7, 11, 7, 29, 3, 5, 3, 5, 17, 11, 3, 23, 3, 7, 37, 5, 3, 3, 13, 5, 5, 41, 83, 3, 43, 7, 5, 29, 11, 89, 3, 11, 5, 23, 3, 3
OFFSET
1,1
LINKS
FORMULA
From Amiram Eldar, Jul 18 2024:
a(n) = A053575(A066669(n)).
a(n) = A000265(A000010(A066669(n))) = A006530(A000010(A066669(n))). (End)
EXAMPLE
A066669(9) = 23, phi(23) = 2*11, so a(9)=11.
MATHEMATICA
Select[Array[#/2^IntegerExponent[#, 2] &@ EulerPhi@ # &, 200], PrimeQ] (* Michael De Vlieger, Dec 08 2018 *)
PROG
(PARI) lista(nn) = {for (n=1, nn, en=eulerphi(n); if (isprime(p=en>>valuation(en, 2)), print1(p, ", ")); ); } \\ Michel Marcus, Dec 08 2018
KEYWORD
nonn
AUTHOR
Labos Elemer, Dec 18 2001
STATUS
approved