Right half of Pascal's triangle.

Terms

a(0) =1a(1) =1a(2) =2a(3) =1a(4) =3a(5) =1a(6) =6a(7) =4a(8) =1a(9) =10a(10) =5a(11) =1a(12) =20a(13) =15a(14) =6a(15) =1a(16) =35a(17) =21a(18) =7a(19) =1a(20) =70a(21) =56a(22) =28a(23) =8a(24) =1a(25) =126a(26) =84a(27) =36a(28) =9a(29) =1