Number of trees with 3-colored leaves.

Terms

a(0) =1a(1) =3a(2) =6a(3) =6a(4) =16a(5) =39a(6) =114a(7) =335a(8) =1081a(9) =3574a(10) =12408a(11) =44076a(12) =160915a(13) =598244a(14) =2263400a(15) =8681464a(16) =33713947a(17) =132305267a(18) =524095596a(19) =2093208435a(20) =8422013745a(21) =34110403728a(22) =138979989162a(23) =569339728312