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

Terms

a(0) =0a(1) =1a(2) =2a(3) =12a(4) =48a(5) =360a(6) =2160a(7) =20160a(8) =161280a(9) =1814400a(10) =18144000a(11) =239500800a(12) =2874009600a(13) =43589145600a(14) =610248038400