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A005642
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Number of 2-diregular connected digraphs with n nodes.
(Formerly M2689)
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0
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1, 3, 7, 24, 117, 663, 4824, 40367, 381554, 4001849, 46043780, 576018785, 7783281188, 112953364381, 1752128923245, 28930230194371, 506596534953769
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,2
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REFERENCES
| M. V. S. Ramanath; T. R. Walsh, Enumeration and generation of a class of regular digraphs, J. Graph Theory 11 (1987), no. 4, 471-479.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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CROSSREFS
| Sequence in context: A007172 A027610 A135688 * A019055 A041045 A041563
Adjacent sequences: A005639 A005640 A005641 * A005643 A005644 A005645
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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