E.g.f.: Product_{k>=1} (1 + x^(3*k-2) / (3*k-2)).

Terms

a(0) =1a(1) =1a(2) =0a(3) =0a(4) =6a(5) =30a(6) =0a(7) =720a(8) =5760a(9) =0a(10) =362880a(11) =5417280a(12) =17107200a(13) =479001600a(14) =8885479680a(15) =32691859200