1249280domain: NAppears in sequencesa(0) = 1, a(1) = 3; for n > 1, a(n) = 2*a(n-1) + 4*a(n-2).at n=12A063782A007318 * A000125.at n=14A134396Number of 0..n arrays of length 6 with each element unequal to at least one neighbor, starting with 0.at n=15A221465a(n) = 4^n*(1 + (23/8)*n + (9/8)*n^2).at n=7A361609