Expansion of e.g.f.: exp((1+x)^3 - 1).

Terms

a(0) =1a(1) =3a(2) =15a(3) =87a(4) =585a(5) =4383a(6) =35919a(7) =318195a(8) =3015441a(9) =30354075a(10) =322626159a(11) =3603292047a(12) =42120047385a(13) =513557128503