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A039743 Number k such that gcd(phi(k), k-1) = number of distinct prime factors of k. 1
2, 4, 8, 15, 16, 32, 35, 39, 51, 55, 63, 64, 70, 75, 87, 95, 99, 111, 115, 119, 123, 128, 130, 135, 143, 147, 154, 155, 159, 171, 183, 187, 203, 207, 215, 219, 235, 238, 256, 267, 275, 279, 280, 287, 291, 295, 299, 303, 310, 319, 322, 323, 327, 335, 339, 351 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Number of primes counted without multiplicity. - Harvey P. Dale, Jun 19 2020
LINKS
EXAMPLE
phi(15)=8, gcd(8,14)=2, 15=3*5, 2 prime factors.
MATHEMATICA
Select[Range[400], GCD[EulerPhi[#], #-1]==PrimeNu[#]&] (* Harvey P. Dale, Jun 19 2020 *)
CROSSREFS
Sequence in context: A076351 A140117 A328677 * A070008 A033623 A094398
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Definition clarified by Harvey P. Dale, Jun 19 2020
STATUS
approved

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Last modified March 3 14:10 EST 2024. Contains 370512 sequences. (Running on oeis4.)