Number of unlabeled rooted trees with 2n + 1 nodes in which all outdegrees are even.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =12a(5) =33a(6) =91a(7) =264a(8) =780a(9) =2365a(10) =7274a(11) =22727a(12) =71784a(13) =229094a(14) =737215a(15) =2390072a(16) =7798020a(17) =25587218a(18) =84377881a(19) =279499063a(20) =929556155a(21) =3102767833a(22) =10390936382a(23) =34903331506a(24) =117564309276a(25) =396994228503