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%I #20 Jul 18 2024 09:18:15
%S 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,
%T 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,
%U 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
%N Primes arising in A066669: the only odd prime divisor of phi(A066669(n)).
%H Michael De Vlieger, <a href="/A066670/b066670.txt">Table of n, a(n) for n = 1..10000</a>
%F From _Amiram Eldar_, Jul 18 2024:
%F a(n) = A053575(A066669(n)).
%F a(n) = A000265(A000010(A066669(n))) = A006530(A000010(A066669(n))). (End)
%e A066669(9) = 23, phi(23) = 2*11, so a(9)=11.
%t Select[Array[#/2^IntegerExponent[#, 2] &@ EulerPhi@ # &, 200], PrimeQ] (* _Michael De Vlieger_, Dec 08 2018 *)
%o (PARI) lista(nn) = {for (n=1, nn, en=eulerphi(n); if (isprime(p=en>>valuation(en, 2)), print1(p, ", ")); ); } \\ _Michel Marcus_, Dec 08 2018
%Y Cf. A000010, A000265, A053575, A006530, A065966, A066669, A066671, A066672, A066673.
%K nonn
%O 1,1
%A _Labos Elemer_, Dec 18 2001