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

Terms

a(0) =1a(1) =1a(2) =2a(3) =1a(4) =3a(5) =1a(6) =6a(7) =1a(8) =5a(9) =10a(10) =1a(11) =6a(12) =20a(13) =6a(14) =1a(15) =21a(16) =35a(17) =7a(18) =1a(19) =28a(20) =70a(21) =28a(22) =1a(23) =9a(24) =84a(25) =126a(26) =36a(27) =1a(28) =10a(29) =120