|
|
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
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|