Number of ordered rooted trees with n generators.

Terms

a(0) =1a(1) =2a(2) =7a(3) =32a(4) =166a(5) =926a(6) =5419a(7) =32816a(8) =203902a(9) =1292612a(10) =8327254a(11) =54358280a(12) =358769152a(13) =2390130038a(14) =16051344307a(15) =108548774240a(16) =738563388214