10890040domain: NAppears in sequencesNumbers n such that sigma(phi(n)) = n.at n=13A018784Numbers k such that sigma(phi(k)) == 0 (mod k).at n=14A067144a(n) = A062402(2^n+1).at n=22A096856a(n) = 27225*n^2 + 2*n.at n=19A157820