Sum{T(i,n-i): i=0,1,...,n}, array T as in A047100.

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =10a(5) =20a(6) =37a(7) =70a(8) =140a(9) =280a(10) =544a(11) =1065a(12) =2130a(13) =4260a(14) =8418a(15) =16684a(16) =33368a(17) =66736a(18) =132760a(19) =264436a(20) =528872a(21) =1057744a(22) =2110233a(23) =4212350a(24) =8424700a(25) =16849400a(26) =33658512a(27) =67254158a(28) =134508316a(29) =269016632