a(n) = Catalan(n-1)*Motzkin(n).

Terms

a(0) =1a(1) =2a(2) =8a(3) =45a(4) =294a(5) =2142a(6) =16764a(7) =138567a(8) =1194050a(9) =10638056a(10) =97383208a(11) =911829646a(12) =8702182020a(13) =84418698600a(14) =830606179680