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A115755
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Number of permutations of n elements whose unsigned reversal distance is k.
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0
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1, 1, 1, 1, 3, 2, 1, 6, 15, 2, 1, 10, 51, 56, 2, 1, 15, 127, 390, 185, 2, 1, 21, 263, 1562, 2543, 648, 2, 1, 28, 483, 4635, 16445, 16615, 2111, 2, 1, 36, 820, 11407, 69863, 169034, 105365, 6352, 2
(list; table; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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REFERENCES
| Kececioglu, J. and Sankoff, D.: Exact and Approximation Algorithms for Sorting by Reversals, with Application to Genome Rearrangement, Algorithmica, 13 (1-2), pp. 180-210, 1995.
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EXAMPLE
| a(3,1) = 3 because the only three permutations of S_3 that require exactly one reversal to be sorted are (1 3 2), (2 1 3) and (3 2 1).
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CROSSREFS
| Sequence in context: A143778 A200536 A164645 * A016556 A067050 A001355
Adjacent sequences: A115752 A115753 A115754 * A115756 A115757 A115758
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KEYWORD
| more,nonn,tabl
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AUTHOR
| Anthony Labarre (alabarre(AT)ulb.ac.be), Mar 29 2006, Jun 03 2006
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