Number of ordered rooted trees on n nodes with thinning limbs.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =10a(5) =25a(6) =68a(7) =187a(8) =530a(9) =1523a(10) =4447a(11) =13121a(12) =39107a(13) =117490a(14) =355507a(15) =1082234a(16) =3312255a(17) =10185125a(18) =31450633a(19) =97480337a(20) =303157086a(21) =945671951a(22) =2958113722a(23) =9276528602a(24) =29158191215a(25) =91845796986a(26) =289874628176a(27) =916536727561