A163055 Number of reduced words of length n in Coxeter group on 12 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.

1, 12, 132, 1452, 15906, 174240, 1908720, 20908800, 229042770, 2509019700, 27484733100, 301077971700, 3298119892650, 36128829891000, 395768617233000, 4335396381723000, 47491541694374250, 520239981289297500

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, -55).

Programs

Mathematica

coxG[{4,55,-10}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Jul 03 2020 *)

Formula

G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(55*t^4 - 10*t^3 - 10*t^2 - 10*t + 1)