First denominator and then numerator of central elements of 1/2-Pascal triangle.

Terms

a(0) =1a(1) =1a(2) =2a(3) =1a(4) =1a(5) =3a(6) =1a(7) =11a(8) =1a(9) =40a(10) =1a(11) =147a(12) =1a(13) =546a(14) =1a(15) =2046a(16) =1a(17) =7722a(18) =1a(19) =29315a(20) =1a(21) =111826a(22) =1a(23) =428298a(24) =1a(25) =1646008a(26) =1a(27) =6344366a(28) =1a(29) =24515700