134401domain: NPropertiesPrimalityPrimeyesAppears in sequencesa(n) = n! * Sum_{d|n} (n/d)^(d-1) / d!.at n=7A354845Primes of the form (2*p^2 + 1)/3 where p is a prime > 3.at n=22A362225Prime numbersat n=12534