A306008 Number of non-isomorphic intersecting set-systems of weight n with no singletons.

1, 0, 1, 1, 2, 3, 7, 10, 21, 39, 78

Offset: 0

Author

Gus Wiseman, Jun 16 2018

Keywords

• nonn
• more

Comments

An intersecting set-system is a finite set of finite nonempty sets (edges), any two of which have a nonempty intersection. The weight of a set-system is the sum of cardinalities of its elements. Weight is generally not the same as number of vertices.

Examples

			Non-isomorphic representatives of the a(6) = 7 set-systems:
{{1,2,3,4,5,6}}
{{1,5},{2,3,4,5}}
{{3,4},{1,2,3,4}}
{{1,2,5},{3,4,5}}
{{1,3,4},{2,3,4}}
{{1,2},{1,3},{2,3}}
{{1,4},{2,4},{3,4}}
		

Crossrefs

Cf. A007716, A034691, A048143, A049311, A116540, A283877, A293606, A293607, A304867, A305999, A305854-A305857, A306005-A306007.