Sum{T(i,n-i): i=0,1,...,n}, array T as in A047150.

Terms

a(0) =1a(1) =2a(2) =4a(3) =6a(4) =12a(5) =24a(6) =42a(7) =84a(8) =168a(9) =336a(10) =672a(11) =1240a(12) =2480a(13) =4960a(14) =9471a(15) =18942a(16) =37884a(17) =75768a(18) =151536a(19) =292344a(20) =584688a(21) =1169376a(22) =2287951a(23) =4575902a(24) =9151804a(25) =18303608a(26) =36607216a(27) =71849311a(28) =143698622a(29) =287397244