
COMMENTS

Corresponding values of factorials are 1!, 2!, 3!, 5!, 7!, 8!, 9!, 11! and 13!, respectively.
This sequence is complete by Saunders, Theorem 1.
All integers in this sequence are square. Hence, there exists no mth power with m >= 3 whose totient is a factorial except 1.
More generally, Saunders, Theorem 1 states that, for any positive integers a, b, c, m with gcd(b, c) = 1, there are only finitely many solutions to phi(ax^m) = b*n!/c and these solutions satisfy n <= max {61, 3a, 3b, 3c}.
