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A164631
Number of reduced words of length n in Coxeter group on 19 generators S_i with relations (S_i)^2 = (S_i S_j)^7 = I.
0
1, 19, 342, 6156, 110808, 1994544, 35901792, 646232085, 11632174452, 209379084903, 3768822534060, 67838787717588, 1221097856797728, 21979755624219696, 395635496869474254, 7121437065054388737
OFFSET
0,2
COMMENTS
The initial terms coincide with those of A170738, 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)/(153*t^7 - 17*t^6 - 17*t^5 - 17*t^4 - 17*t^3 - 17*t^2 - 17*t + 1).
MATHEMATICA
coxG[{7, 153, -17}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Aug 27 2017 *)
CROSSREFS
Sequence in context: A163110 A163453 A163968 * A164909 A165341 A165881
KEYWORD
nonn
AUTHOR
John Cannon and N. J. A. Sloane, Dec 03 2009
STATUS
approved