A164628 Number of reduced words of length n in Coxeter group on 17 generators S_i with relations (S_i)^2 = (S_i S_j)^7 = I.

1, 17, 272, 4352, 69632, 1114112, 17825792, 285212536, 4563398400, 73014339720, 1168228880640, 18691653212160, 299066309345280, 4785058676736000, 76560902463178680, 1224973857577579200, 19599572411913213000

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,-120).

Programs

Mathematica

coxG[{7,120,-15}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Nov 13 2015 *)

Formula

G.f.: (t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(120*t^7 - 15*t^6 - 15*t^5 - 15*t^4 - 15*t^3 - 15*t^2 - 15*t + 1).