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A326372
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Number of intersecting antichains of (possibly empty) subsets of {1..n}.
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3
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OFFSET
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0,1
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COMMENTS
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A set system (set of sets) is an antichain if no edge is a subset of any other, and is intersecting if no two edges are disjoint.
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LINKS
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FORMULA
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EXAMPLE
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The a(0) = 2 through a(3) = 13 antichains:
{} {} {} {}
{{}} {{}} {{}} {{}}
{{1}} {{1}} {{1}}
{{2}} {{2}}
{{1,2}} {{3}}
{{1,2}}
{{1,3}}
{{2,3}}
{{1,2,3}}
{{1,2},{1,3}}
{{1,2},{2,3}}
{{1,3},{2,3}}
{{1,2},{1,3},{2,3}}
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CROSSREFS
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The case without empty edges is A001206.
The inverse binomial transform is the spanning case A305844.
Maximal intersecting antichains are A326363.
Intersecting set systems are A051185.
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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