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A004122
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Generalized weak orders on n points.
(Formerly M2064)
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4
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2, 13, 123, 1546, 24283, 457699, 10064848, 252945467, 7151532895, 224661610888, 7763387794649, 292659248485051, 11951855446598278, 525645673381008537, 24769319755329986599, 1244984053628241578058, 66487872534167725541751
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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REFERENCES
| I. P. Goulden and D. M. Jackson, Combinatorial Enumeration, John Wiley and Sons, N.Y., 1983.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
C. G. Wagner, Enumeration of generalized weak orders. Arch. Math. (Basel) 39 (1982), no. 2, 147-152.
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..100
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FORMULA
| E.g.f. : 1/(2-exp(x)*exp(exp(x)-1)).
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MATHEMATICA
| With[{nn=20}, Rest[CoefficientList[Series[1/(2-Exp[x]Exp[Exp[x]-1]), {x, 0, nn}], x] Range[0, nn]!]] (* From Harvey P. Dale, Nov 05 2011 *)
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CROSSREFS
| Cf. A004121, A004123, A000670.
Sequence in context: A110369 A000180 A192460 * A086630 A151361 A073559
Adjacent sequences: A004119 A004120 A004121 * A004123 A004124 A004125
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KEYWORD
| nonn,nice,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| Formula and more terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Mar 27 2001
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