A164860 Number of reduced words of length n in Coxeter group on 15 generators S_i with relations (S_i)^2 = (S_i S_j)^8 = I.

1, 15, 210, 2940, 41160, 576240, 8067360, 112943040, 1581202455, 22136832900, 309915640125, 4338818675100, 60743457438300, 850408347952800, 11905716084771600, 166680014174856000, 2333520044280745320

Offset: 0

Author

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

Keywords

• nonn

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.

Links

• Index entries for linear recurrences with constant coefficients, signature (13, 13, 13, 13, 13, 13, 13, -91).

Programs

Mathematica

coxG[{8,91,-13}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Apr 05 2022 *)

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)/(91*t^8 -

13*t^7 - 13*t^6 - 13*t^5 - 13*t^4 - 13*t^3 - 13*t^2 - 13*t + 1)