364941domain: NAppears in sequencesNumbers k such that phi(k) is equal to A008473(k).at n=27A039779Numbers k such that phi(k) = Sum_{d|k} core(d) where core(x) is the squarefree part of x (A007913).at n=27A074786Numbers k such that sigma(k)^2 = psi(k)^2 + phi(k)^2.at n=4A389593