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A162925
Number of reduced words of length n in Coxeter group on 5 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.
0
1, 5, 20, 80, 310, 1200, 4650, 18000, 69690, 269820, 1044630, 4044420, 15658470, 60623640, 234711810, 908715240, 3518201250, 13621143060, 52735907790, 204173464860, 790482339630, 3060448278480, 11848896802170, 45874441471680
OFFSET
0,2
COMMENTS
The initial terms coincide with those of A003947, although the two sequences are eventually different.
Computed with MAGMA using commands similar to those used to compute A154638.
FORMULA
G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(6*t^4 - 3*t^3 - 3*t^2 - 3*t + 1)
MATHEMATICA
coxG[{4, 6, -3, 30}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Oct 28 2023 *)
CROSSREFS
Sequence in context: A117422 A154639 A214939 * A163316 A163878 A164354
KEYWORD
nonn
AUTHOR
John Cannon and N. J. A. Sloane, Dec 03 2009
STATUS
approved