Number of rooted trees with 2-colored leaves.

Terms

a(0) =2a(1) =2a(2) =5a(3) =13a(4) =37a(5) =108a(6) =332a(7) =1042a(8) =3360a(9) =11019a(10) =36722a(11) =123875a(12) =422449a(13) =1453553a(14) =5040816a(15) =17599468a(16) =61814275a(17) =218252584a(18) =774226549a(19) =2758043727a(20) =9862357697a(21) =35387662266a(22) =127374191687a(23) =459783039109