Sum{T(i,n-i): i=0,1,...,n}, array T given by A047000.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =8a(5) =15a(6) =30a(7) =52a(8) =101a(9) =202a(10) =376a(11) =740a(12) =1480a(13) =2840a(14) =5625a(15) =11250a(16) =21928a(17) =43583a(18) =87166a(19) =171420a(20) =341412a(21) =682824a(22) =1350144a(23) =2692536a(24) =5385072a(25) =10684872a(26) =21326481a(27) =42652962a(28) =84825224a(29) =169403773