150343domain: NPropertiesPrimalityPrimeyesAppears in sequencesPrimes base 10 that remain primes in six bases b, 2<=b<=10, expansions interpreted as decimal numbers.at n=21A052028Smaller of two consecutive prime numbers such that p1*p2*d - d = average of twin prime pairs, d (delta) = p2 - p1.at n=20A153378Prime numbersat n=13879