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A306007 Number of non-isomorphic intersecting antichains of weight n. 8
1, 1, 1, 1, 2, 2, 6, 6, 14, 22 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,5
COMMENTS
An intersecting antichain S is a finite set of finite nonempty sets (edges), any two of which have a nonempty intersection, and none of which is a subset of any other. The weight of S is the sum of cardinalities of its elements. Weight is generally not the same as number of vertices.
LINKS
EXAMPLE
Non-isomorphic representatives of the a(8) = 14 set-systems:
{{1,2,3,4,5,6,7,8}}
{{1,7},{2,3,4,5,6,7}}
{{1,2,7},{3,4,5,6,7}}
{{1,5,6},{2,3,4,5,6}}
{{1,2,3,7},{4,5,6,7}}
{{1,2,5,6},{3,4,5,6}}
{{1,3,4,5},{2,3,4,5}}
{{1,2},{1,3,4},{2,3,4}}
{{1,4},{1,5},{2,3,4,5}}
{{1,5},{2,4,5},{3,4,5}}
{{1,6},{2,6},{3,4,5,6}}
{{1,6},{2,3,6},{4,5,6}}
{{2,4},{1,2,5},{3,4,5}}
{{1,5},{2,5},{3,5},{4,5}}
CROSSREFS
Sequence in context: A056453 A244486 A309800 * A287603 A034422 A140833
KEYWORD
nonn,more
AUTHOR
Gus Wiseman, Jun 16 2018
STATUS
approved

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Last modified March 28 17:25 EDT 2024. Contains 371254 sequences. (Running on oeis4.)