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A003025
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Number of n-node labeled acyclic digraphs with 1 out-point.
(Formerly M2083)
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6
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1, 2, 15, 316, 16885, 2174586, 654313415, 450179768312, 696979588034313, 2398044825254021110, 18151895792052235541515, 299782788128536523836784628, 10727139906233315197412684689421
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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REFERENCES
| 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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EXAMPLE
| a(2) = 2: o-->--o (2 ways)
a(3) = 15: o-->--o-->--o (6 ways) and
o ... o o-->--o
.\ . / . \ . /
. v v ... v v
.. o ..... o
(3 ways) (6 ways)
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CROSSREFS
| Cf. A058876, A003026.
Sequence in context: A076111 A087526 A059167 * A015200 A030642 A175563
Adjacent sequences: A003022 A003023 A003024 * A003026 A003027 A003028
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Apr 10 2001
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