96907domain: NPropertiesPrimalityPrimeyesAppears in sequencesNumber of bracelets of length n using exactly two different colored beads.at n=21A056342Primes p such that q=2*p^2-1, r=2*p*q-1 and 2*p*r-1 are also prime.at n=3A224991Prime numbersat n=9328