E.g.f.: 1 / (1 + x^3/3 + log(1 - x)).

Terms

a(0) =1a(1) =1a(2) =3a(3) =12a(4) =72a(5) =534a(6) =4818a(7) =50532a(8) =606408a(9) =8182656a(10) =122712912a(11) =2024328096a(12) =36432644400a(13) =710346495312