520209

Appears in sequences

• a(1)=1, a(2)=2, a(n)=a(n-1)+floor(a(n-2)*a(n-1)/(a(n-2)+a(n-1))).at n=39A173090
• Numbers with 4 or more prime factors (with multiplicity) such that every concatenation of their prime factors is prime.at n=19A217265