Number of trees with 3-colored nodes.

Terms

a(0) =1a(1) =3a(2) =6a(3) =18a(4) =75a(5) =342a(6) =1773a(7) =9894a(8) =58596a(9) =362061a(10) =2314119a(11) =15185223a(12) =101830986a(13) =695253993a(14) =4819762446a(15) =33851833506a(16) =240472935735