159072domain: NAppears in sequencesa(n) = Sum_{k=0..m} T(n,k) * T(n,k+2), where m=2 for n=2 and m=n+1 for n >= 3; and T is given by A026148.at n=5A027331Half the number of 0..n arrays of length 4 with second differences nonzero.at n=22A212783