E.g.f.: 1 / ((1 - x)*(2 - exp(x))).

Terms

a(0) =1a(1) =2a(2) =7a(3) =34a(4) =211a(5) =1596a(6) =14259a(7) =147106a(8) =1722683a(9) =22591408a(10) =328161643a(11) =5232410646a(12) =90880495347