Triangular array formed from elements to left of middle of Pascal's triangle.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =1a(5) =4a(6) =1a(7) =5a(8) =10a(9) =1a(10) =6a(11) =15a(12) =1a(13) =7a(14) =21a(15) =35a(16) =1a(17) =8a(18) =28a(19) =56a(20) =1a(21) =9a(22) =36a(23) =84a(24) =126a(25) =1a(26) =10a(27) =45a(28) =120a(29) =210