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Search: id:A092238
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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
1
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OFFSET
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1,3
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COMMENT
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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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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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Sequence in context: A085535 A060613 A139772 this_sequence A003358 A041511 A002604
Adjacent sequences: A092235 A092236 A092237 this_sequence A092239 A092240 A092241
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KEYWORD
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more,nonn
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AUTHOR
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R. P. Stanley (rstan(AT)math.mit.edu), Feb 19 2004
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