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A013981
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Number of commutative elements in Coxeter group H_n.
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0
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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REFERENCES
| 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
| binomial(2*n+2, n+1)-2^(n+2)+n+3;
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CROSSREFS
| Sequence in context: A055824 A020113 A163650 * A199308 A176479 A162356
Adjacent sequences: A013978 A013979 A013980 * A013982 A013983 A013984
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KEYWORD
| nonn
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AUTHOR
| C. Kenneth Fan (ckfan(AT)MATH.HARVARD.EDU)
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