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Search: id:A125307
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| A125307 |
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Number of increasing trees with branches of height 1. |
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+0
1
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| 1, 1, 4, 15, 80, 480, 3444, 27790, 253504, 2556792, 28382880, 343071168, 4490999424, 63253633872, 954133373088, 15343385194800, 262060291958784, 4737396899952384, 90370907329842432, 1814141041750834560, 38229440785429201920, 843786230514306621696
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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Permutations avoiding a nonconsecutive 132 pattern. - Ralf Stephan, May 09 2007
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REFERENCES
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R. P. Stanley, Enumerative Combinatorics, Vol. 1, Cambridge University Press, 1997. Proposition 1.3.16, p25.
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LINKS
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D. Callan, Permutations avoiding a nonconsecutive instance of a 2- or 3-letter pattern
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FORMULA
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E.g.f.: (x-1+ln(1-x)) / ( (x-1)^2 (ln(1-x)-1) ).
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MATHEMATICA
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Range[0, 21]!CoefficientList[ Series[(x - 1 + Log[1 - x])/((1 - x)^2(Log[1 - x] - 1)), {x, 0, 21}], x] (* Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 26 2007 *)
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CROSSREFS
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Sequence in context: A002467 A111726 A090376 this_sequence A073479 A147690 A068313
Adjacent sequences: A125304 A125305 A125306 this_sequence A125308 A125309 A125310
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KEYWORD
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nonn
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AUTHOR
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Wenjin Woan (wjwoan(AT)hotmail.com), Jan 17 2007
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EXTENSIONS
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More terms from N. J. A. Sloane (njas(AT)research.att.com), Jan 26 2007
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