a(n) = round(Gamma(n+1/3)/Gamma(1/3)).

Terms

a(0) =1a(1) =0a(2) =0a(3) =1a(4) =3a(5) =15a(6) =80a(7) =506a(8) =3710a(9) =30920a(10) =288591a(11) =2982109a(12) =33797241a(13) =416832633a(14) =5557768440a(15) =79661347641