OFFSET
1,1
COMMENTS
The only odd terms below 10^7 are 3, 5, 17, 257 & 65537.
PROG
(PARI) u(n)=sumdivmult(n, d, if(gcd(d, n/d)==1, d));
for(n=1, 10^5, if(isprime(u(eulerphi(n))), print1(n, ", "))); \\ Joerg Arndt, Sep 17 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Dec 07 2001
EXTENSIONS
Deleted incorrect MMA program. - N. J. A. Sloane, Sep 17 2023
STATUS
approved