Number of non-isomorphic set-systems of weight n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =9a(5) =18a(6) =44a(7) =98a(8) =244a(9) =605a(10) =1595a(11) =4273a(12) =12048a(13) =34790a(14) =104480a(15) =322954a(16) =1031556a(17) =3389413a(18) =11464454a(19) =39820812a(20) =141962355a(21) =518663683a(22) =1940341269a(23) =7424565391a(24) =29033121685a(25) =115921101414a(26) =472219204088