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A092238
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Number of ways to write the permutation n,n-1,...,1 of 1,2,...,n as a product of n(n-1)/2 transpositions, where each transposition of 1,2,...,n occurs exactly once.
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0
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OFFSET
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0,4
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COMMENTS
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If we impose the additional condition on the product t_1 t_2 ... of transpositions that the number of inversions increases by one each time we multiply by a t_i, then the number of ways is given by A005118.
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LINKS
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Table of n, a(n) for n=0..6.
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EXAMPLE
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a(3)=2 because 321 = (1,2)(1,3)(2,3) = (2,3)(1,3)(1,2).
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CROSSREFS
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Cf. A005118.
Sequence in context: A085535 A060613 A139772 * A228252 A339305 A337651
Adjacent sequences: A092235 A092236 A092237 * A092239 A092240 A092241
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KEYWORD
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more,nonn
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AUTHOR
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Richard Stanley, Feb 19 2004
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EXTENSIONS
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a(0)=1 prepended and a(6) added by Alois P. Heinz, Jul 12 2017
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STATUS
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approved
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