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Search: id:A059523
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| A059523 |
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Number of n-element unlabeled ordered T_0-antichains without isolated vertices; number of T_1-hypergraphs (without empty edge and without multiple edges) on n labeled vertices. |
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+0
1
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| 1, 2, 2, 36, 19020, 2010231696, 9219217412568364176, 170141181796805105960861096082778425120, 57896044618658097536026644159052312977171804852352892309392604715987334365792
(list; graph; listen)
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OFFSET
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0,2
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REFERENCES
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G. Kilibarda and V. Jovovic, "Enumeration of some classes of T_0-hypergraphs", in preparation, 2004.
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LINKS
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V. Jovovic, T_1-hyper graphs on a labeled 3-set
Goran Kilibarda and Vladeta Jovovic, Antichains of Multisets, J. Integer Seqs., Vol. 7, 2004.
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FORMULA
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a(n)=A059052(n)/2.
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EXAMPLE
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Number of k-element T_1-hipergraphs (without empty edge and without multiple edges) on 3 labeled vertices is
C(7,k)-6*C(5,k)+6*C(4,k)+3*C(3,k)-6*C(2,k)+2*C(1,k),k=0..7; so a(3)=2+11+15+7+1=36=2^7-6*2^5+6*2^4+3*2^3-6*2^2+2*2.
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CROSSREFS
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Cf. A003465, A059201, A059052.
Sequence in context: A056612 A131658 A131657 this_sequence A038623 A001121 A116567
Adjacent sequences: A059520 A059521 A059522 this_sequence A059524 A059525 A059526
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KEYWORD
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nonn
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AUTHOR
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Vladeta Jovovic and Goran Kilibarda (vladeta(AT)Eunet.yu), Jan 20 2001; revised Jun 03 2004
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