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A327070
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Number of non-connected simple labeled graphs covering n vertices.
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14
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1, 0, 0, 0, 3, 40, 745, 21028, 973889, 80133088, 12523299729, 3847333778244, 2341705361100633, 2821794389863015840, 6728707109106848947081, 31769173063866390661714996, 297278309767391164611330317921
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OFFSET
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0,5
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COMMENTS
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We consider the empty graph to be neither connected (one component) nor disconnected (more than one component).
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LINKS
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FORMULA
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Inverse binomial transform of A327199.
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EXAMPLE
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The a(4) = 3 graphs:
{{1,2},{3,4}}
{{1,3},{2,4}}
{{1,4},{2,3}}
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MATHEMATICA
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csm[s_]:=With[{c=Select[Tuples[Range[Length[s]], 2], And[OrderedQ[#], UnsameQ@@#, Length[Intersection@@s[[#]]]>0]&]}, If[c=={}, s, csm[Sort[Append[Delete[s, List/@c[[1]]], Union@@s[[c[[1]]]]]]]]];
Table[Length[Select[Subsets[Subsets[Range[n], {2}]], Union@@#==Range[n]&&Length[csm[#]]!=1&]], {n, 0, 5}]
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CROSSREFS
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The non-covering version is A327199.
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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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