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Search: id:A001373
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| A001373 |
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Functional digraphs (digraphs of functions on n nodes where every node has outdegree 1 and loops of length 1 are forbidden).
(Formerly M1597 N0623)
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+0
6
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| 1, 0, 1, 2, 6, 13, 40, 100, 291, 797, 2273, 6389, 18264, 51916, 148666, 425529, 1221900, 3511507, 10111043, 29142941, 84112009, 243000149, 702758065, 2034150215, 5892907566, 17084615940, 49567063847, 143902155133
(list; graph; listen)
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OFFSET
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0,4
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REFERENCES
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F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 70, Table 3.4.1.
R. C. Read, Note on number of functional digraphs, Math. Ann., vol. 143 (1961), pp. 109-111.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
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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N. J. A. Sloane, Transforms
L. Travis, [math/9811127] Graphical Enumeration: A Species-Theoretic Approach
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CROSSREFS
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Euler transform of A002862. Cf. A001372.
Sequence in context: A026550 A124124 A052450 this_sequence A057243 A012470 A056592
Adjacent sequences: A001370 A001371 A001372 this_sequence A001374 A001375 A001376
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KEYWORD
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nonn,nice,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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Sequence extended by Paul Zimmermann; more terms and better description from Christian Bower.
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