Expansion of e.g.f.: exp(2*x)/(1-x).

Terms

a(0) =1a(1) =3a(2) =10a(3) =38a(4) =168a(5) =872a(6) =5296a(7) =37200a(8) =297856a(9) =2681216a(10) =26813184a(11) =294947072a(12) =3539368960a(13) =46011804672a(14) =644165281792