E.g.f. 1 + x*exp(x) + x^2*exp(2*x).

Terms

a(0) =1a(1) =1a(2) =4a(3) =15a(4) =52a(5) =165a(6) =486a(7) =1351a(8) =3592a(9) =9225a(10) =23050a(11) =56331a(12) =135180a(13) =319501a(14) =745486a(15) =1720335a(16) =3932176a(17) =8912913a(18) =20054034a(19) =44826643a(20) =99614740a(21) =220200981a(22) =484442134a(23) =1061158935a(24) =2315255832a(25) =5033164825