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A164815 Number of reduced words of length n in Coxeter group on 13 generators S_i with relations (S_i)^2 = (S_i S_j)^8 = I. 0
1, 13, 156, 1872, 22464, 269568, 3234816, 38817792, 465813426, 5589760176, 67077110958, 804925197648, 9659100765600, 115909189913088, 1390910047667712, 16690917796540416, 200290980252825462 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
The initial terms coincide with those of A170732, although the two sequences are eventually different.
Computed with MAGMA using commands similar to those used to compute A154638.
LINKS
FORMULA
G.f.: (t^8 + 2*t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(66*t^8 - 11*t^7 - 11*t^6 - 11*t^5 - 11*t^4 - 11*t^3 - 11*t^2 - 11*t + 1)
MATHEMATICA
With[{num=Total[2t^Range[7]]+t^8+1, den=Total[-11 t^Range[7]]+66t^8+1}, CoefficientList[Series[num/den, {t, 0, 30}], t]] (* Harvey P. Dale, Aug 21 2011 *)
CROSSREFS
Sequence in context: A163438 A163958 A164610 * A165269 A165873 A166377
KEYWORD
nonn
AUTHOR
John Cannon and N. J. A. Sloane, Dec 03 2009
STATUS
approved

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Last modified June 19 09:16 EDT 2024. Contains 373494 sequences. (Running on oeis4.)