Riordan matrix (1/sqrt(1-4*x),x/(1-x)).

Terms

a(0) =1a(1) =2a(2) =1a(3) =6a(4) =3a(5) =1a(6) =20a(7) =9a(8) =4a(9) =1a(10) =70a(11) =29a(12) =13a(13) =5a(14) =1a(15) =252a(16) =99a(17) =42a(18) =18a(19) =6a(20) =1a(21) =924a(22) =351a(23) =141a(24) =60a(25) =24a(26) =7a(27) =1a(28) =3432a(29) =1275