"BHK" (reversible, identity, unlabeled) transform of A035353.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =5a(5) =15a(6) =44a(7) =140a(8) =442a(9) =1443a(10) =4751a(11) =15903a(12) =53716a(13) =183334a(14) =630513a(15) =2184417a(16) =7614318a(17) =26690344a(18) =94015908a(19) =332639104a(20) =1181596784a(21) =4212424485a(22) =15066677338a(23) =54050993664a(24) =194438337125a(25) =701224890628