22931219729domain: NAppears in sequencesWrite down all the prime divisors in previous term.at n=7A006919a(1) = 1; for n > 1, if a(n-1) is composite then a(n) is the concatenation of all the prime factors in order of a(n-1), otherwise a(n) is the smallest number not yet appearing in the sequence.at n=17A331603