Number of directed rooted trees with n nodes.

Terms

a(0) =1a(1) =3a(2) =15a(3) =82a(4) =495a(5) =3144a(6) =20875a(7) =142773a(8) =1000131a(9) =7136812a(10) =51702231a(11) =379234623a(12) =2810874950a(13) =21020047557a(14) =158398829121