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

0,2

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

Table of n, a(n) for n=0..15.

Index entries for linear recurrences with constant coefficients, signature (25,25,25,-325).

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).

Prog

(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

Crossrefs

Sequence in context: A157461 A342037 A162827 * A163527 A164017 A164644

Adjacent sequences: A163176 A163177 A163178 * A163180 A163181 A163182

Keyword

nonn

Author

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

Status

approved