E.g.f.: Product_{k>=1} (1 + x^(3*k-1) / (3*k-1)).

Terms

a(0) =1a(1) =0a(2) =1a(3) =0a(4) =0a(5) =24a(6) =0a(7) =504a(8) =5040a(9) =0a(10) =226800a(11) =3628800a(12) =0a(13) =438721920a(14) =6227020800a(15) =16345929600