Number of unordered pairs of rooted trees with a total of n nodes and an even total of leaves.

Terms

a(0) =0a(1) =1a(2) =1a(3) =2a(4) =3a(5) =8a(6) =18a(7) =49a(8) =120a(9) =313a(10) =802a(11) =2120a(12) =5591a(13) =14942a(14) =40033a(15) =108108a(16) =293094a(17) =798839a(18) =2185341a(19) =6002085a(20) =16538599a(21) =45716952a(22) =126727195a(23) =352215812a(24) =981268481a(25) =2739930091a(26) =7666333161a(27) =21491833976a(28) =60358490615a(29) =169798048026