512430domain: NAppears in sequencesNumbers k such that sigma(phi(k)) - phi(k) = phi(sigma(k)), where phi(k) is the Euler totient function of k and sigma(k) is the sum of the divisors of k.at n=34A271633G.f. A(x) satisfies: A(x) = 1 - Sum_{k=1..3} (x * A(x))^k.at n=21A337512