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

Terms

a(0) =1a(1) =3a(2) =15a(3) =103a(4) =897a(5) =9471a(6) =117703a(7) =1685475a(8) =27361953a(9) =497111707a(10) =10001175231a(11) =220849928223