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A180962
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Number of linear extensions for Young-Fibonacci lattices of increasing rank
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0
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OFFSET
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1,3
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REFERENCES
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Donald E. Knuth, The Art of Computer Programming, Volume 4 Fascicle 2, Generating All Tuples and Permutations (2005), v+128pp. ISBN 0-201-85393-0. [Algorithm V for generating all topological sorts.]
Richard P. Stanley, "Differential posets," Journal of the American Mathematical Society Vol. 1, No. 4, pp. 919-961, 1988.
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LINKS
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Table of n, a(n) for n=1..6.
Frank Ruskey, The Combinatorial Object Server (Implementation of Varol-Rotem algorithm). http://theory.cs.uvic.ca/inf/pose/LinearExt.html
Wikipedia, Young-Fibonacci lattice
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EXAMPLE
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For n = 3, the Young-Fibonacci lattice as defined by the following edge set {(1,2),(2,3),(2,4)} has two total orderings: 1234 and 1243. The sequence increases rapidly since Young-Fibonacci lattices are sparse digraphs.
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CROSSREFS
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Sequence in context: A138834 A088321 A061301 * A092798 A068916 A093987
Adjacent sequences: A180959 A180960 A180961 * A180963 A180964 A180965
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KEYWORD
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nonn
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AUTHOR
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Nikolaos Kavvadias, Jan 23 2011
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STATUS
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approved
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