Sum{T(i,n-i): i=0,1,...,n}, array T as in A047030.

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =9a(5) =18a(6) =32a(7) =63a(8) =124a(9) =245a(10) =490a(11) =964a(12) =1923a(13) =3835a(14) =7652a(15) =15304a(16) =30504a(17) =60973a(18) =121866a(19) =243596a(20) =487192a(21) =973568a(22) =1946851a(23) =3893037a(24) =7784919a(25) =15569838a(26) =31132592a(27) =62262654a(28) =124519328a(29) =249028126