OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
108 is not a square, phi(108)=36, 3 is the squarefree part of 108 and 3 divides 36. Hence a(9)=108 is in the sequence.
MATHEMATICA
f[p_, e_] := (p - 1)*p^((e - 1) - Mod[e, 2]); q[n_] := ! AllTrue[(fct = FactorInteger[n])[[;; , 2]], EvenQ] && IntegerQ[Times @@ f @@@ fct]; Select[Range[2, 1250], q] (* Amiram Eldar, Mar 09 2021 *)
PROG
(PARI) isok(m) = !issquare(m) && !(eulerphi(m) % core(m)); \\ Michel Marcus, Nov 30 2020
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 13 2002
EXTENSIONS
Name edited by Michel Marcus, Nov 30 2020
STATUS
approved