717025domain: NAppears in sequencesPseudoprimes to base 7 that are not squarefree.at n=20A243089Nonsquarefree numbers n = p_1^s_1...p_m^s_m (m > 1) such that (p_i^s_i - 1) | n-1 for all 0 < i <= m.at n=12A292815The numbers k for which Lucas(k) are Niven numbers.at n=37A337449