E.g.f.: exp(x*(1 - x^3 + x^4)/(1-x)).

Terms

a(0) =1a(1) =1a(2) =3a(3) =13a(4) =49a(5) =381a(6) =2971a(7) =26713a(8) =291873a(9) =3262969a(10) =41245651a(11) =569262981a(12) =8433896593a(13) =136060620853