A066670 Primes arising in A066669: the only odd prime divisor of phi(A066669(n)).

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

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

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

Crossrefs

Cf. A000010, A000265, A053575, A006530, A065966, A066669, A066671, A066672, A066673.

Sequence in context: A077924 A003569 A333596 * A282270 A013606 A372041

Adjacent sequences: A066667 A066668 A066669 * A066671 A066672 A066673

Keyword

nonn

Author

Labos Elemer, Dec 18 2001

Status

approved