66507086889domain: NAppears in sequencesa(n) = a(n-1) + 4*a(n-2), a(0) = a(1) = 1.at n=27A006131a(n) = Sum_{k=0..floor(n/2)} binomial(n-k, k-1) * 4^(k-1).at n=28A099580a(n) = 9*a(n-1) - 16*a(n-2), with a(0) = 1, a(1) = 9.at n=13A102902