220918domain: NAppears in sequencesSemiprimes in A103378.at n=25A103398Semiprimes in A103379.at n=26A103399Semiprimes in A103380.at n=27A103400a(n) = A027306(n) + A027306(n-1) for n > 0; a(0) = 1.at n=18A248574