3988424domain: NAppears in sequencesNumbers k such that the multiplicative group of residues prime to k, M_k, is isomorphic to M_{k+1}.at n=12A003276Numbers n such that n-th prime - phi(n) - d(n) = (n+1)-th prime - phi(n+1) - d(n+1), where d(n) = number of divisors of n.at n=14A063690