A164781 Number of reduced words of length n in Coxeter group on 12 generators S_i with relations (S_i)^2 = (S_i S_j)^8 = I.

1, 12, 132, 1452, 15972, 175692, 1932612, 21258732, 233845986, 2572305120, 28295348400, 311248745280, 3423735239760, 37661077095840, 414271732097520, 4556987777548800, 50126851522277970, 551395212406754100

Offset: 0

Author

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

Keywords

• nonn

Comments

The initial terms coincide with those of A003954, 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 (10, 10, 10, 10, 10, 10, 10, -55).

Programs

Mathematica

coxG[{8, 55, -10}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Oct 17 2015 *)

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)/(55*t^8 - 10*t^7 - 10*t^6 - 10*t^5 - 10*t^4 - 10*t^3 - 10*t^2 - 10*t + 1).