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A003431
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Number of connected irreducible posets with n labeled points.
(Formerly M4857)
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4
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0, 1, 0, 0, 1, 12, 104, 956, 10037, 126578, 1971005, 38569954, 958347642, 30400603560, 1234260982770, 64187360439352, 4275470549123119
(list;
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history;
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OFFSET
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0,6
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REFERENCES
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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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Table of n, a(n) for n=0..16.
S. R. Finch, Series-parallel networks
S. R. Finch, Series-parallel networks, July 7, 2003. [Cached copy, with permission of the author]
R. P. Stanley, Enumeration of posets generated by disjoint unions and ordinal sums, Proc. Amer. Math. Soc. 45 (1974), 295-299.
R. P. Stanley, Letter to N. J. A. Sloane, c. 1991
J. A. Wright, Letter to N. J. A. Sloane, Apr 06 1972, listing 18 sequences
Index entries for sequences related to posets
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CROSSREFS
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Cf. A003430, A046906.
Sequence in context: A024454 A222540 A279301 * A173835 A334168 A220111
Adjacent sequences: A003428 A003429 A003430 * A003432 A003433 A003434
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KEYWORD
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nonn,nice,more
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AUTHOR
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N. J. A. Sloane and Richard Stanley
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EXTENSIONS
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More terms from Richard Stanley, Jun 19 2003
2 more terms from Vladeta Jovovic, Feb 17 2008
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STATUS
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approved
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