Number of different hierarchical orderings that can be formed from n unlabeled elements with no repetition of subhierarchies.

A098407

Number of different hierarchical orderings that can be formed from n unlabeled elements with no repetition of subhierarchies.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =6a(4) =13a(5) =33a(6) =78a(7) =186a(8) =436a(9) =1028a(10) =2394a(11) =5566a(12) =12877a(13) =29689a(14) =68198a(15) =156194a(16) =356599a(17) =811959a(18) =1843956a(19) =4177436a(20) =9442166a(21) =21295934a(22) =47932572a(23) =107677140a(24) =241443980a(25) =540441068a(26) =1207689636a(27) =2694452060a(28) =6002389882a(29) =13351958546

External references