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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..10000

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

CROSSREFS

Cf. A000010, A066669, A066671, A066672, A066673, A065966.

Sequence in context: A302141 A077924 A003569 * A282270 A013606 A206550

Adjacent sequences:  A066667 A066668 A066669 * A066671 A066672 A066673

KEYWORD

nonn

AUTHOR

Labos Elemer, Dec 18 2001

STATUS

approved

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Last modified May 29 03:06 EDT 2020. Contains 334696 sequences. (Running on oeis4.)