1640250000domain: NAppears in sequencesNumbers k = p_i^e_i *...* p_r^e_r such that i/e_i +...+ r/e_r = 1 for e_i,..., e_r >= 1; p_i,..., p_r distinct prime numbers (A000040).at n=23A388006Powers k^m, m > 1, where k is an Achilles number that has a primorial kernel but is not a product of primorials.at n=21A389374