Number of rooted trees with n nodes, most of which are not leaves.

Terms

a(0) =0a(1) =0a(2) =1a(3) =1a(4) =5a(5) =7a(6) =28a(7) =48a(8) =176a(9) =336a(10) =1179a(11) =2420a(12) =8269a(13) =17855a(14) =59832a(15) =134289a(16) =443407a(17) =1025685a(18) =3346702a(19) =7933161a(20) =25632265a(21) =62000170a(22) =198670299a(23) =488801159a(24) =1555187172a(25) =3882403641a(26) =12276230777a(27) =31034921462a(28) =97601239282a(29) =249471619165