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A048200
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Minimal length pair-exchange / set-rotate sequence to reverse n distinct ordered elements.
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2
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OFFSET
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1,3
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COMMENTS
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"Rotate" is always a left-rotate (moves leftmost element to the right end) and "Exchange" is always a pair-exchange of the two leftmost elements.
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LINKS
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Table of n, a(n) for n=1..10.
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EXAMPLE
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a(4) = 4 since "xrrx" is the shortest sequence reversing "ABCD". Explicitly, (begin) ABCD, (x)-> BACD, (r)-> ACDB, (r) -> CDBA, (x)-> DCBA.
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CROSSREFS
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Sequence in context: A080149 A217134 A128513 * A058201 A000947 A218211
Adjacent sequences: A048197 A048198 A048199 * A048201 A048202 A048203
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KEYWORD
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nonn,nice,more
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AUTHOR
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Tony Bartoletti
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EXTENSIONS
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55 added by Tony Bartoletti, Feb 22 2011
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STATUS
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approved
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