Number of trees on n vertices with an even number of leaves.

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =1a(5) =2a(6) =3a(7) =6a(8) =12a(9) =25a(10) =54a(11) =120a(12) =278a(13) =657a(14) =1586a(15) =3885a(16) =9676a(17) =24350a(18) =61974a(19) =159066a(20) =411637a(21) =1072477a(22) =2812147a(23) =7414611a(24) =19650656a(25) =52319946a(26) =139898593a(27) =375536661a(28) =1011726481a(29) =2734793731