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A049524
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Number of digraphs with a source and a sink on n labeled nodes.
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7
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1, 3, 48, 3424, 962020, 1037312116, 4344821892264, 71771421308713624, 4716467927380427847264, 1237465168798883061207535456, 1297923989772809185944542332007104, 5444330658513426322624322033259452670016, 91342931436147421630261703458729460990513248512
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OFFSET
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1,2
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COMMENTS
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Here a source is defined to be a node which has a directed path to all other nodes and a sink to be a node to which all other nodes have a directed path. A digraph with a source and a sink can also be described as initially-finally connected. - Andrew Howroyd, Jan 16 2022
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REFERENCES
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V. Jovovic, G. Kilibarda, Enumeration of labeled initially-finally connected digraphs, Scientific review, Serbian Scientific Society, 19-20 (1996), p. 244.
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LINKS
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PROG
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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