5781222721

Appears in sequences

• a(1) = 561; a(n+1) = smallest Fermat pseudoprime to all natural bases up to lpf(a(n)).at n=22A300629
• a(n) is the smallest Carmichael number k such that gpf(p-1) = prime(n) for all prime factors p of k.at n=12A327787
• Carmichael numbers k for which bigomega(phi(k)) < bigomega(k-1), where bigomega gives the number of prime divisors, counted with multiplicity.at n=16A339909
• Records in A083876.at n=22A348258