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Search: id:A020561
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| A020561 |
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Number of ordered oriented multigraphs on n labeled arcs (with loops). |
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+0
2
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| 1, 2, 17, 252, 5535, 165278, 6355147, 303080956, 17440307953, 1185613611362, 93640428880873, 8476453909912332, 869565923845396207, 100138764123162257470, 12840593975018953569971, 1820531766301308581051116, 283643668353734597645391393
(list; graph; listen)
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OFFSET
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0,2
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REFERENCES
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G. Labelle, Counting enriched multigraphs..., Discrete Math., 217 (2000), 237-248.
G. Paquin, D\'enombrement de multigraphes enrichis, M\'emoire, Math. Dept., Univ. Qu\'ebec \`a Montr\'eal, 2004.
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FORMULA
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Sum_{k=0..n} abs(Stirling1(n, k))*Bell(2*k). - Vladeta Jovovic (vladeta(AT)eunet.rs), Jun 21 2003
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CROSSREFS
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Sequence in context: A099694 A099698 A098622 this_sequence A099702 A029735 A037896
Adjacent sequences: A020558 A020559 A020560 this_sequence A020562 A020563 A020564
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KEYWORD
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nonn
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AUTHOR
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Gilbert Labelle (gilbert(AT)lacim.uqam.ca), Simon Plouffe (simon.plouffe(AT)gmail.com)
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