Duplicate of A007226.

Terms

a(0) =2a(1) =3a(2) =10a(3) =42a(4) =198a(5) =1001a(6) =5304a(7) =29070a(8) =163438a(9) =937365a(10) =5462730a(11) =32256120a(12) =192565800