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A306006 Number of non-isomorphic intersecting set-systems of weight n. 27
1, 1, 1, 2, 3, 5, 10, 16, 30, 57 (list; graph; refs; listen; history; text; internal format)
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 * A047011 A259393 A018163

Adjacent sequences:  A306003 A306004 A306005 * A306007 A306008 A306009

KEYWORD

nonn,more

AUTHOR

Gus Wiseman, Jun 16 2018

STATUS

approved

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Last modified February 20 19:57 EST 2020. Contains 332084 sequences. (Running on oeis4.)