Triangular array formed by taking every other term of each row of Pascal's triangle.

Terms

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