A164868 Number of reduced words of length n in Coxeter group on 17 generators S_i with relations (S_i)^2 = (S_i S_j)^8 = I.

1, 17, 272, 4352, 69632, 1114112, 17825792, 285212672, 4563402616, 73014439680, 1168231000200, 18691695448320, 299067118295040, 4785073750671360, 76561177737953280, 1224978807442636800, 19599660337248356280

Offset: 0

Author

John Cannon and N. J. A. Sloane, Dec 03 2009

Keywords

• nonn

Comments

The initial terms coincide with those of A170736, although the two sequences are eventually different.

Computed with MAGMA using commands similar to those used to compute A154638.

Links

• Index entries for linear recurrences with constant coefficients, signature (15, 15, 15, 15, 15, 15, 15, -120).

Programs

Mathematica

coxG[{8,120,-15}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Jul 07 2019 *)

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)/(120*t^8 -

15*t^7 - 15*t^6 - 15*t^5 - 15*t^4 - 15*t^3 - 15*t^2 - 15*t + 1)