32240122domain: NAppears in sequencesa(n) = Sum_{k=0..floor(2*n/3)} binomial(k+2,2) * binomial(k,2*n-3*k).at n=33A392269a(n) = Sum_{k=0..n} binomial(k+2,2) * binomial(k,3*n-3*k).at n=22A392313