3171317360domain: NAppears in sequencesNumber of binary rooted trees of height n requiring 3 registers.at n=13A006223a(n) = Sum_{k=0..n} A033184(n,k)*A033184(n,n-k), where Catalan triangle entry A033184(n,k) = C(2*n-k,n-k)*(k+1)/(n+1).at n=13A143388