OFFSET
1,2
COMMENTS
If k and phi(k) are both not squarefree then k is in the list.
A prime p is in the list if p - 1 is squarefree and bigomega(p - 1) = A001222(p - 1) is odd.
It follows that the subsequence of primes is A078330. - Bernard Schott, Apr 03 2021
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
8 is in the list since mu(8) = 0 and mu(phi(8)) = mu(4) = 0.
7 is not in the list since mu(7) = -1 and mu(phi(7)) = mu(6) = 1.
MATHEMATICA
Select[Range[200], MoebiusMu[#] == MoebiusMu[EulerPhi[#]] &] (* Alonso del Arte, Feb 16 2015 *)
PROG
(Sage)
[n for n in [1..1000] if moebius(n)==moebius(euler_phi(n))]
(PARI) for(n=1, 140, if(moebius(n) == moebius(eulerphi(n)), print1(n, ", "))) \\ Indranil Ghosh, Mar 11 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Tom Edgar, Feb 16 2015
STATUS
approved