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A003028
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Number of digraphs on n labeled nodes with a source.
(Formerly M3157)
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8
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1, 3, 51, 3614, 991930, 1051469032, 4366988803688, 71895397383029040, 4719082081411731363408, 1237678715644664931691596416, 1297992266840866792981316221144960, 5444416466164313011147841248189209354496, 91343356480627224177654291875698256656613808896
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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REFERENCES
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V. Jovovic and G. Kilibarda, Enumeration of labeled initially-finally connected digraphs, Scientific review, Serbian Scientific Society, 19-20 (1996) 237-247.
R. W. Robinson, Counting labeled acyclic digraphs, pp. 239-273 of F. Harary, editor, New Directions in the Theory of Graphs. Academic Press, NY, 1973.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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Andrew Howroyd, Table of n, a(n) for n = 1..50
V. Jovovic and G. Kilibarda, Enumeration of labeled quasi-initially connected digraphs, Discrete Math., 224 (2000), 151-163.
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PROG
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(PARI) Initially(12) \\ See A057274. - Andrew Howroyd, Jan 11 2022
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CROSSREFS
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The unlabeled version is A051421.
Row sums of A057274.
Cf. A003027, A003029, A003030, A049524, A049414, A350792.
Sequence in context: A172434 A210676 A105639 * A069343 A084882 A275798
Adjacent sequences: A003025 A003026 A003027 * A003029 A003030 A003031
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KEYWORD
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nonn,easy,nice
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AUTHOR
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N. J. A. Sloane
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EXTENSIONS
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Corrected and extended by Vladeta Jovovic, Goran Kilibarda
Terms a(12) and beyond from Andrew Howroyd, Jan 11 2022
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STATUS
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approved
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