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A164634
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Number of reduced words of length n in Coxeter group on 21 generators S_i with relations (S_i)^2 = (S_i S_j)^7 = I.
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0
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1, 21, 420, 8400, 168000, 3360000, 67200000, 1343999790, 26879991600, 537599748210, 10751993288400, 215039832252000, 4300795974720000, 86015906088000000, 1720317853632043890, 34406351710082593500
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OFFSET
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0,2
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COMMENTS
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The initial terms coincide with those of A170740, although the two sequences are eventually different.
Computed with MAGMA using commands similar to those used to compute A154638.
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LINKS
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FORMULA
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G.f.: (t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(190*t^7 - 19*t^6 - 19*t^5 - 19*t^4 - 19*t^3 - 19*t^2 - 19*t + 1).
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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