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A007453
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Number of connected N-free posets with n nodes.
(Formerly M2813)
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2
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1, 1, 3, 9, 30, 103, 375, 1400, 5380, 21073, 83950, 338878, 1383576, 5702485, 23696081, 99163323, 417553252, 1767827220, 7520966100, 32135955585, 137849390424, 593407692685, 2562695780058, 11099806544050, 48206136562750
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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REFERENCES
| P. J. Cameron, Some sequences of integers, Discrete Math., 75 (1989), 89-102; also in "Graph Theory and Combinatorics 1988", ed. B. Bollobas, Annals of Discrete Math., 43 (1989), 89-102.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| Index entries for sequences related to posets
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CROSSREFS
| Sequence in context: A148951 A047007 A047064 * A148952 A148953 A148954
Adjacent sequences: A007450 A007451 A007452 * A007454 A007455 A007456
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KEYWORD
| nonn,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Mira Bernstein
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