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Search: id:A013981
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| A013981 |
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Number of commutative elements in Coxeter group H_n. |
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+0
1
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| 1, 2, 9, 44, 195, 804, 3185, 12368, 47607, 182720, 701349, 2695978, 10384231, 40083848, 155052001, 600949336, 2333344095, 9074611032, 35344215245, 137844431690, 538253680159, 2104090575136, 8233413950409
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OFFSET
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0,2
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REFERENCES
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C. Kenneth Fan, Structure of a Hecke algebra quotient. J. Amer. Math. Soc. 10 (1997), no. 1, 139-167.
C. K. Fan, A Hecke algebra quotient and some combinatorial applications. J. Algebraic Combin. 5 (1996), no. 3, 175-189.
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MAPLE
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binomial(2*n+2, n+1)-2^(n+2)+n+3;
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CROSSREFS
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Sequence in context: A055824 A020113 A163650 this_sequence A162356 A026302 A124889
Adjacent sequences: A013978 A013979 A013980 this_sequence A013982 A013983 A013984
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KEYWORD
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nonn
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AUTHOR
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C. Kenneth Fan (ckfan(AT)MATH.HARVARD.EDU)
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