4483008515domain: NAppears in sequencesa(n) = 4*a(n-1) - 4*a(n-2) + 3*a(n-3).at n=21A099215a(n) = 3*a(n-1) - a(n-3) + 3*a(n-4), with initial values 1,3,9,11.at n=21A135365