Expansion of e.g.f. (1+x-x^3)/((1-x)*(1-x^2)).

Terms

a(0) =1a(1) =2a(2) =6a(3) =18a(4) =96a(5) =480a(6) =3600a(7) =25200a(8) =241920a(9) =2177280a(10) =25401600a(11) =279417600a(12) =3832012800a(13) =49816166400a(14) =784604620800