Sum{T(i,n-i): i=0,1,...,n}, array T as in A047110.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =10a(5) =20a(6) =40a(7) =71a(8) =142a(9) =260a(10) =520a(11) =1040a(12) =1936a(13) =3872a(14) =7330a(15) =14660a(16) =29320a(17) =55874a(18) =111748a(19) =215252a(20) =430504a(21) =861008a(22) =1663662a(23) =3327324a(24) =6476960a(25) =12953920a(26) =25907840a(27) =50511295a(28) =101022590a(29) =198016168