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A212417
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Size of the equivalence class of S_n containing the identity permutation under transformations of positionally adjacent elements of the form abc <--> acb <--> bac where a<b<c.
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8
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OFFSET
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0,4
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LINKS
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J. Cassaigne, M. Espie, D. Krob, J.-C. Novelli, F. Hivert, The Chinese Monoid, Int'l. J. Algebra and Comp. 11 (2001), 301-334.
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EXAMPLE
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a(3) = 3: {123, 132, 213}.
a(4) = 7: {1234, 1243, 1324, 1423, 2134, 2143, 2314}. (End)
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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