The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 Harvey P. Dale, Table of n, a(n) for n = 1..1000 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 Cf. A000010, A001221. Sequence in context: A076351 A140117 A328677 * A070008 A033623 A094398 Adjacent sequences: A039740 A039741 A039742 * A039744 A039745 A039746 KEYWORD nonn,easy AUTHOR Olivier Gérard EXTENSIONS Definition clarified by Harvey P. Dale, Jun 19 2020 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

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