Expansion of e.g.f. exp(x + x^3).

Terms

a(0) =1a(1) =1a(2) =1a(3) =7a(4) =25a(5) =61a(6) =481a(7) =2731a(8) =10417a(9) =91225a(10) =681121a(11) =3493711a(12) =33597961a(13) =303321877a(14) =1938378625a(15) =20282865331a(16) =211375647841