a(n) = floor(Gamma(n + 2/3)/Gamma(2/3)).

Terms

a(0) =1a(1) =0a(2) =1a(3) =2a(4) =10a(5) =50a(6) =287a(7) =1915a(8) =14684a(9) =127262a(10) =1230201a(11) =13122149a(12) =153091744a(13) =1939162100a(14) =26501882045a(15) =388694270000