13959773domain: NPropertiesPrimalityPrimeyesAppears in sequencesa(n) = 1 + 2 * (a(n-1) + a(n-4) + a(n-6)) + a(n-7) for n>3, with initial values 0 if n<0, and 1,3,8,18 for n=0..3.at n=20A317188Prime numbersat n=907678