E.g.f.: exp(3*x + x^2/2).

Terms

a(0) =1a(1) =3a(2) =10a(3) =36a(4) =138a(5) =558a(6) =2364a(7) =10440a(8) =47868a(9) =227124a(10) =1112184a(11) =5607792a(12) =29057400a(13) =154465704a(14) =841143312a(15) =4685949792a(16) =26674999056a(17) =155000193840a(18) =918475565472