Riordan array (1, x(1-x)/(1-3x)).

Terms

a(0) =1a(1) =0a(2) =1a(3) =0a(4) =2a(5) =1a(6) =0a(7) =6a(8) =4a(9) =1a(10) =0a(11) =18a(12) =16a(13) =6a(14) =1a(15) =0a(16) =54a(17) =60a(18) =30a(19) =8a(20) =1a(21) =0a(22) =162a(23) =216a(24) =134a(25) =48a(26) =10a(27) =1a(28) =0a(29) =486