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

Terms

a(0) =1a(1) =2a(2) =9a(3) =64a(4) =617a(5) =7446a(6) =107377a(7) =1795844a(8) =34114929a(9) =724822282a(10) =17018900921a(11) =437402060712