413138881domain: NAppears in sequencesa(1) = 561; a(n+1) = smallest Fermat pseudoprime to all natural bases up to lpf(a(n)).at n=18A300629Carmichael numbers k for which bigomega(phi(k)) < bigomega(k-1), where bigomega gives the number of prime divisors, counted with multiplicity.at n=6A339909Records in A083876.at n=18A348258