Number of rooted identity trees with n generators.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =10a(5) =27a(6) =77a(7) =226a(8) =685a(9) =2112a(10) =6618a(11) =20996a(12) =67337a(13) =217884a(14) =710571a(15) =2332958a(16) =7705429a(17) =25584035a(18) =85346018a(19) =285908169a(20) =961440343a(21) =3244259406a(22) =10981797187a(23) =37280278698a(24) =126890974820a(25) =432950169885