Number of series-reduced noncrossing trees with n edges.

Terms

a(0) =1a(1) =1a(2) =0a(3) =4a(4) =5a(5) =33a(6) =91a(7) =408a(8) =1485a(9) =6195a(10) =24838a(11) =103752a(12) =432796a(13) =1834140a(14) =7815900a(15) =33591376a(16) =145197017a(17) =631281591a(18) =2757917260a(19) =12102728740a(20) =53321334381a(21) =235768155073