A306006 Number of non-isomorphic intersecting set-systems of weight n.

1, 1, 1, 2, 3, 5, 10, 16, 30, 57

Offset

0,4

Comments

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

Links

Table of n, a(n) for n=0..9.

Example

Non-isomorphic representatives of the a(6) = 10 set-systems:
{{1,2,3,4,5,6}}
{{5},{1,2,3,4,5}}
{{1,5},{2,3,4,5}}
{{3,4},{1,2,3,4}}
{{1,2,5},{3,4,5}}
{{1,3,4},{2,3,4}}
{{3},{2,3},{1,2,3}}
{{4},{1,4},{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-A306008.

Sequence in context: A118728 A062860 A024369 * A364641 A047011 A359518

Adjacent sequences: A306003 A306004 A306005 * A306007 A306008 A306009

Keyword

nonn,more

Author

Gus Wiseman, Jun 16 2018

Status

approved