140103domain: NAppears in sequencesPerfect totient numbers.at n=28A082897Perfect totient numbers, omitting powers of 3.at n=18A091847O.g.f. satisfies: A(x) = Sum_{n>=0} (n+2)^n * x^n * A(n*x)^n/n! * exp(-(n+2)*x*A(n*x)).at n=6A221411