OFFSET
1,1
COMMENTS
Primes p with mu(p-1)=0, where mu is the Möbius function. - T. D. Noe, Nov 03 2003
Primes p such that the sum of the primitive roots of p (see A088144) is 0 mod p. - Jon Wharf, Mar 12 2015
The relative density of this sequence within the primes is 1 - A005596 = 0.626044... - Amiram Eldar, Feb 10 2021
LINKS
T. D. Noe, Table of n, a(n) for n=1..1000
Eric Weisstein's World of Mathematics, Moebius Function.
FORMULA
a(n) = A145199(n) + 1. - Amiram Eldar, Feb 10 2021
EXAMPLE
p = 257 is here because p-1 = 256 = 2^8.
p = 997 is here because p-1 = 996 = 3*(2^2)*83.
MATHEMATICA
Select[Prime[Range[400]], MoebiusMu[ #-1]==0&]
PROG
(Magma) [ p: p in PrimesUpTo(500) | not IsSquarefree(p-1) ]; // Vincenzo Librandi, Mar 12 2015
(PARI) forprime(p=2, 500, if(!issquarefree(p-1), print(p))) \\ Michael B. Porter, Mar 16 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved