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A164626
Number of reduced words of length n in Coxeter group on 15 generators S_i with relations (S_i)^2 = (S_i S_j)^7 = I.
0
1, 15, 210, 2940, 41160, 576240, 8067360, 112942935, 1581199620, 22136774205, 309914552220, 4338799717980, 60743139868320, 850403171588880, 11905633390308840, 166678713297370365, 2333499827827833210
OFFSET
0,2
COMMENTS
The initial terms coincide with those of A170734, although the two sequences are eventually different.
Computed with MAGMA using commands similar to those used to compute A154638.
FORMULA
G.f.: (t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(91*t^7 - 13*t^6 - 13*t^5 - 13*t^4 - 13*t^3 - 13*t^2 - 13*t + 1).
CROSSREFS
Sequence in context: A163091 A163440 A163962 * A164860 A165282 A165875
KEYWORD
nonn
AUTHOR
John Cannon and N. J. A. Sloane, Dec 03 2009
STATUS
approved