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

Terms

a(0) =1a(1) =4a(2) =18a(3) =92a(4) =536a(5) =3552a(6) =26608a(7) =223456a(8) =2085504a(9) =21450752a(10) =241320704a(11) =2949474816a(12) =38933066752a(13) =552141672448