64160401domain: NAppears in sequencesa(n) = n^6 + n^4 + n^2 + 1.at n=20A059830Numbers of the form k^3+k^2+k+1 that are the product of two distinct primes.at n=21A176070Semiprimes of the form n^3 + n^2 + n + 1.at n=22A237627