Duplicate of A000866.

Terms

a(0) =1a(1) =2a(2) =4a(3) =13a(4) =31a(5) =112a(6) =224a(7) =1003a(8) =2011a(9) =4022a(10) =13044a(11) =31143a(12) =112341a(13) =230232a(14) =1011014