383659domain: NPropertiesPrimalityPrimeyesAppears in sequencesPrimes that remain prime through 4 iterations of function f(x) = 8x + 5.at n=21A023321Primes that are the concatenation p|q of two primes p and q with the same number of digits, where r = (p+q)/2, r|q and p|r are all primes.at n=30A358420Prime numbersat n=32575