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Search: id:A092337
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| A092337 |
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Triangle read by rows: T(n,m) = number of 3-uniform hypergraphs with m hyperedges on n unlabeled nodes, where 0 <= m <= C(n,3). |
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+0
3
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| 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 6, 6, 6, 4, 2, 1, 1, 1, 1, 3, 7, 21, 43, 94, 161, 249, 312, 352, 312, 249, 161, 94, 43, 21, 7, 3, 1, 1, 1, 1, 3, 10, 38, 137, 509, 1760, 5557, 15709, 39433, 87659, 172933, 303277, 473827, 660950, 824410, 920446, 920446, 824410, 660950
(list; graph; listen)
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OFFSET
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3,10
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COMMENT
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A 3-uniform hypergraph is a set of 3-subsets of the nodes with isomorphism determined by permutations of the node set. The numbers are calculated using Polya enumeration from the cycle index of the symmetric group Sym(n) in its action on 3-subsets of an n-set, which can easily be computed by MAGMA or GAP. A000665 is the sum of each row of the triangle.
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REFERENCES
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Palmer, Edgar M. On the number of n-plexes. Discrete Math. 6 (1973), 377-390
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CROSSREFS
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Cf. A000665, A051240.
Sequence in context: A011031 A054584 A049041 this_sequence A050823 A050825 A111150
Adjacent sequences: A092334 A092335 A092336 this_sequence A092338 A092339 A092340
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KEYWORD
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nonn,tabf
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AUTHOR
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Gordon Royle (gordon(AT)maths.uwa.edu.au), Mar 18 2004
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