164073domain: NAppears in sequencesUltra-useful primes: smallest k such that 2^(2^n) - k is prime.at n=18A058220Layer counting sequence in the order-5 cubic honeycomb.at n=8A247308Denominators of r-Egyptian fraction expansion for sqrt(1/2), where r(k) = 1/Prime(k).at n=4A270476Smallest k such that 4^(4^n) - k is prime.at n=9A364452