Duplicate of A026572.

Terms

a(0) =1a(1) =2a(2) =8a(3) =19a(4) =56a(5) =140a(6) =376a(7) =953a(8) =2474a(9) =6286a(10) =16097a(11) =40880a(12) =104069a(13) =264052