209581domain: NPropertiesPrimalityPrimeyesAppears in sequencesNumber of derangements of n elements with one pair repeated exactly once (e.g., "ABABCDEF").at n=6A140526Smallest prime p == 5 (mod 8) such that Q(sqrt(p)) has class number 2n+1.at n=19A355877Prime numbersat n=18771