Number of hierarchical orderings with at least 2 elements on each level for n unlabeled elements. Unlabeled analog of A097236.

A109509

Number of hierarchical orderings with at least 2 elements on each level for n unlabeled elements. Unlabeled analog of A097236.

Terms

    a(0) =1a(1) =0a(2) =1a(3) =1a(4) =3a(5) =4a(6) =9a(7) =14a(8) =28a(9) =47a(10) =88a(11) =152a(12) =279a(13) =486a(14) =876a(15) =1539a(16) =2744a(17) =4824a(18) =8551a(19) =15023a(20) =26503a(21) =46509a(22) =81747a(23) =143210a(24) =251007a(25) =438915a(26) =767403a(27) =1339487a(28) =2336955a(29) =4071906

External references