E.g.f.: exp( x*(1 + exp(2*x)) ).

Terms

a(0) =1a(1) =2a(2) =8a(3) =44a(4) =288a(5) =2192a(6) =18976a(7) =182912a(8) =1934848a(9) =22231808a(10) =275203584a(11) =3645178880a(12) =51370694656a(13) =766634946560