cp's OEIS Frontend

A319764 Number of non-isomorphic intersecting set systems of weight n with empty intersection.

%I A319764 #5 Sep 28 2018 15:22:29
%S A319764 1,0,0,0,0,0,1,1,3,8,18
%N A319764 Number of non-isomorphic intersecting set systems of weight n with empty intersection.
%C A319764 A set system is a finite set of finite nonempty sets. It is intersecting if no two parts are disjoint. The weight of a set system is the sum of sizes of its parts. Weight is generally not the same as number of vertices.
%e A319764 Non-isomorphic representatives of the a(6) = 1 through a(9) = 8 set systems:
%e A319764 6: {{1,2},{1,3},{2,3}}
%e A319764 7: {{1,3},{1,4},{2,3,4}}
%e A319764 8: {{1,2},{1,3,4},{2,3,4}}
%e A319764    {{1,4},{1,5},{2,3,4,5}}
%e A319764    {{2,4},{1,2,5},{3,4,5}}
%e A319764 9: {{1,3},{1,4,5},{2,3,4,5}}
%e A319764    {{1,5},{1,6},{2,3,4,5,6}}
%e A319764    {{2,5},{1,2,6},{3,4,5,6}}
%e A319764    {{1,2,3},{2,4,5},{3,4,5}}
%e A319764    {{1,3,5},{2,3,6},{4,5,6}}
%e A319764    {{1,2},{1,3},{1,4},{2,3,4}}
%e A319764    {{1,2},{1,3},{2,3},{1,2,3}}
%e A319764    {{1,3},{1,4},{3,4},{2,3,4}}
%Y A319764 Cf. A007716, A281116, A283877, A305854, A306006, A316980, A317752, A317755, A317757, A318715, A318717.
%Y A319764 Cf. A319752, A319759, A319762, A319763, A319765, A319779, A319781.
%K A319764 nonn,more
%O A319764 0,9
%A A319764 _Gus Wiseman_, Sep 27 2018