Number of Greg trees with n black nodes.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =5a(5) =12a(6) =37a(7) =116a(8) =412a(9) =1526a(10) =5995a(11) =24284a(12) =101619a(13) =434402a(14) =1893983a(15) =8385952a(16) =37637803a(17) =170871486a(18) =783611214a(19) =3625508762a(20) =16906577279a(21) =79395295122a(22) =375217952457