Number of non-isomorphic set-systems of weight n with at least one endpoint.

Terms

a(0) =0a(1) =1a(2) =2a(3) =4a(4) =8a(5) =18a(6) =40a(7) =94a(8) =228a(9) =579a(10) =1508a(11) =4092a(12) =11478a(13) =33337a(14) =100016a(15) =309916a(16) =990008a(17) =3257196a(18) =11021851a(19) =38314009a(20) =136657181a(21) =499570867a(22) =1869792499a(23) =7158070137a(24) =28003286261a(25) =111857491266a(26) =455852284867