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A304986
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Number of labeled clutters (connected antichains) spanning some subset of {1,...,n}, if clutters of the form {{x}} are allowed for any vertex x.
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8
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OFFSET
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0,2
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LINKS
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FORMULA
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EXAMPLE
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The a(3) = 12 clutters:
{}
{{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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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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