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 A322704 Number of regular hypergraphs on n labeled vertices with no singletons. 3
 1, 1, 2, 4, 80, 209944 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS We define a hypergraph to be any finite set of finite nonempty sets. A hypergraph is regular if all vertices have the same degree. LINKS EXAMPLE The a(3) = 4 edge-sets:   {}   {{1,2,3}}   {{1,2},{1,3},{2,3}}   {{1,2},{1,3},{2,3},{1,2,3}} MATHEMATICA Table[Sum[SeriesCoefficient[Product[1+Times@@x/@s, {s, Subsets[Range[n], {2, n}]}], Sequence@@Table[{x[i], 0, k}, {i, n}]], {k, 0, 2^n-n-1}], {n, 1, 5}] CROSSREFS Cf. A058891, A059441, A295193, A306021, A319189, A319190, A319612, A319729, A322698. Sequence in context: A018389 A092932 A102663 * A076961 A012439 A012435 Adjacent sequences:  A322701 A322702 A322703 * A322705 A322706 A322707 KEYWORD nonn,more AUTHOR Gus Wiseman, Dec 23 2018 STATUS approved

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Last modified April 5 06:06 EDT 2020. Contains 333238 sequences. (Running on oeis4.)