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

Terms

a(0) =0a(1) =0a(2) =2a(3) =12a(4) =74a(5) =540a(6) =4682a(7) =47292a(8) =545834a(9) =7087260a(10) =102247562a(11) =1622632572a(12) =28091567594a(13) =526858348380