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Search: id:A054761
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| A054761 |
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Number of positive braids with n crossings of 5 strands. |
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+0
3
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| 1, 4, 13, 37, 99, 254, 636, 1567, 3822, 9261, 22346
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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The (n+1)-strand braid group B_{n+1} has n generators s_1,...,s_n with relations s_i s_k s_i = s_k s_i s_k for k=i+1, s_i s_k = s_k s_i for k>i+1. The elements are the isotopy classes of (n+1) free strands that are planarily "mixed" (s_i corresponds to the operation of crossing the i-th strand under the (i+1)-th strand)..
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REFERENCES
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F. A. Garside, The braid group and other groups, Quart. Journal Math. Oxford, 1969
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CROSSREFS
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Cf. A000071, A054480.
Adjacent sequences: A054758 A054759 A054760 this_sequence A054762 A054763 A054764
Sequence in context: A003727 A103082 A048474 this_sequence A080145 A097551 A095126
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KEYWORD
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nonn
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AUTHOR
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Serge Burckel (burckel(AT)univ-reunion.fr), Apr 27 2000
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