Sum along upward diagonal of Pascal triangle from center.

Terms

a(0) =1a(1) =0a(2) =1a(3) =2a(4) =1a(5) =3a(6) =7a(7) =4a(8) =11a(9) =25a(10) =16a(11) =41a(12) =92a(13) =63a(14) =155a(15) =344a(16) =247a(17) =591a(18) =1300a(19) =967a(20) =2267a(21) =4950a(22) =3785a(23) =8735a(24) =18955a(25) =14820a(26) =33775a(27) =72905a(28) =58060a(29) =130965