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A001927
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Number of connected partially ordered sets with n labeled points.
(Formerly M2043 N0809)
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4
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1, 1, 2, 12, 146, 3060, 101642, 5106612, 377403266, 40299722580, 6138497261882, 1320327172853172, 397571105288091506, 166330355795371103700, 96036130723851671469482, 76070282980382554147600692, 82226869197428315925408327266
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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REFERENCES
| K. K.-H. Butler and G. Markowsky, Enumeration of finite topologies, Proc. 4th S-E Conf. Combin., Graph Theory, Computing, Congress. Numer. 8 (1973), 169-184.
M. Erne', Struktur- und Anzahlformeln fuer Topologien auf Endlichen Mengen, Manuscripta Math., 11 (1974), 221-259.
M. Erne' and K. Stege, Counting Finite Posets and Topologies, Order, 8 (1991), 247-265.
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
| G. Brinkmann, B. D. McKay, Posets on up to 16 Points, Order 19 (2) (2002) 147-179 (Table II, up to 18 points)
Index entries for sequences related to posets
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FORMULA
| E.g.f. A(x)=log(B(x)) where B(x) is e.g.f. of A001035.
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CROSSREFS
| Cf. A000112, A001035, A000608, A066303.
Sequence in context: A035049 A010790 A086928 * A105558 A126777 A126345
Adjacent sequences: A001924 A001925 A001926 * A001928 A001929 A001930
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KEYWORD
| nonn,nice,hard
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Christian G. Bower (bowerc(AT)usa.net), Dec 12 2001
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