OFFSET
1,2
COMMENTS
Note that k=1 is excluded from the count. - Michel Marcus, Feb 22 2021
LINKS
Max Alekseyev, PARI/GP Scripts for Miscellaneous Math Problems: invphi.gp, 2005-2019.
PROG
(PARI) a(n) = {my(v = invphi(n), m = if (#v, vecmax(v), n)); sum(i=2, m, Mod(eulerphi(i), i) == n); } \\ Michel Marcus, Feb 22 2021; needs invphi.gp
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Jan 24 2002
EXTENSIONS
More terms from Michel Marcus, Feb 22 2021
STATUS
approved