19707683773domain: NAppears in sequencesFor p = prime(n), a(n) is the smallest prime q such that pq is a base-2 pseudoprime; that is, 2^(pq-1) = 1 mod pq; a(n) is 0 if no such prime exists.at n=43A085012Largest prime factor of 2^(2*n+1)+2^(n+1)+1.at n=23A229768