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A165693
Number of reduced words of length n in Coxeter group on 42 generators S_i with relations (S_i)^2 = (S_i S_j)^9 = I.
0
1, 42, 1722, 70602, 2894682, 118681962, 4865960442, 199504378122, 8179679503002, 335366859622221, 13750041244475760, 563751691022059680, 23113819331845141200, 947666592603219256320, 38854330296632296661040
OFFSET
0,2
COMMENTS
The initial terms coincide with those of A170761, although the two sequences are eventually different.
Computed with MAGMA using commands similar to those used to compute A154638.
FORMULA
G.f. (t^9 + 2*t^8 + 2*t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t +
1)/(820*t^9 - 40*t^8 - 40*t^7 - 40*t^6 - 40*t^5 - 40*t^4 - 40*t^3 -
40*t^2 - 40*t + 1)
MATHEMATICA
coxG[{9, 820, -40}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Nov 05 2017 *)
CROSSREFS
Sequence in context: A164112 A164686 A165174 * A166230 A166436 A166716
KEYWORD
nonn
AUTHOR
John Cannon and N. J. A. Sloane, Dec 03 2009
STATUS
approved