Sum along upward diagonal of Pascal triangle from (but not including) halfway point.

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =1a(5) =3a(6) =7a(7) =14a(8) =11a(9) =25a(10) =51a(11) =97a(12) =92a(13) =189a(14) =365a(15) =674a(16) =709a(17) =1383a(18) =2587a(19) =4685a(20) =5270a(21) =9955a(22) =18228a(23) =32551a(24) =38403a(25) =70954a(26) =127921a(27) =226007a(28) =276408a(29) =502415