Number of rooted Greg trees.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =78a(5) =313a(6) =1306a(7) =5653a(8) =25088a(9) =113685a(10) =523522a(11) =2443590a(12) =11533010a(13) =54949539a(14) =263933658a(15) =1276652682a(16) =6213207330a(17) =30402727854a(18) =149486487326a(19) =738184395770