5681809domain: NAppears in sequencesStrong pseudoprimes (base-2) equal to product of 3 primes not necessarily distinct.at n=20A112450Base-2 Fermat pseudoprimes k such that the multiplicative order of 2 modulo k is odd.at n=31A367230Composite numbers k such that 2^(2^(k-1)-1) == 1 (mod k^2).at n=14A376253