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

Terms

a(0) =0a(1) =0a(2) =1a(3) =1a(4) =1a(5) =1a(6) =6a(7) =7a(8) =8a(9) =9a(10) =38a(11) =47a(12) =57a(13) =68a(14) =245a(15) =313a(16) =393a(17) =486a(18) =1594a(19) =2080a(20) =2673a(21) =3388a(22) =10429a(23) =13817a(24) =18058a(25) =23307a(26) =68497a(27) =91804a(28) =121541a(29) =159081