E.g.f.: exp(x+x^2+x^3+x^4).

Terms

a(0) =1a(1) =1a(2) =3a(3) =13a(4) =73a(5) =381a(6) =2611a(7) =19993a(8) =165873a(9) =1436473a(10) =14004451a(11) =145099461a(12) =1584090553a(13) =18196817653a(14) =223416271443