A163179 Number of reduced words of length n in Coxeter group on 27 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.

1, 27, 702, 18252, 474201, 12320100, 320085675, 8316067500, 216057716550, 5613342710625, 145838884522500, 3789004401804375, 98441196968058750, 2557576669978687500, 66447774146243953125, 1726363373899181062500

Offset: 0

Author

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

Keywords

• nonn

Comments

The initial terms coincide with those of A170746, 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 (25,25,25,-325).

Programs

PARI

Vec((t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(325*t^4 - 25*t^3 - 25*t^2 - 25*t + 1) + O(t^20)) \\ Jinyuan Wang, Mar 23 2020

Formula

G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(325*t^4 - 25*t^3 - 25*t^2 - 25*t + 1).