A164983 Number of reduced words of length n in Coxeter group on 30 generators S_i with relations (S_i)^2 = (S_i S_j)^8 = I.

1, 30, 870, 25230, 731670, 21218430, 615334470, 17844699630, 517496288835, 15007392363600, 435214378179000, 12621216956594400, 366015291433936200, 10614443442672409200, 307818859579059389400, 8926746920297948448000

Offset: 0

Author

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

Keywords

• nonn

Comments

The initial terms coincide with those of A170749, 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 (28, 28, 28, 28, 28, 28, 28, -406).

Programs

Mathematica

coxG[{8,406,-28}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Oct 27 2016 *)

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)/(406*t^8 -

28*t^7 - 28*t^6 - 28*t^5 - 28*t^4 - 28*t^3 - 28*t^2 - 28*t + 1)