OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
k such that abs(mu(k)) = 1 and abs(mu(phi(k))) = 1.
EXAMPLE
86 is here because it is squarefree and the same holds for phi(86) = 42.
MATHEMATICA
Select[Range[500], And@@SquareFreeQ/@{#, EulerPhi[#]}&] (* Harvey P. Dale, Nov 05 2013 *)
PROG
(Magma) [n:n in [1..500]| IsSquarefree(n) and IsSquarefree(EulerPhi(n))]; // Marius A. Burtea, Jul 11 2019
(PARI) isok(m) = issquarefree(m) && issquarefree(eulerphi(m)); \\ Michel Marcus, Jul 12 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved