A163175 Number of reduced words of length n in Coxeter group on 25 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.

1, 25, 600, 14400, 345300, 8280000, 198547500, 4761000000, 114164729700, 2737573095600, 65644673871900, 1574103433035600, 37745661174674100, 905108843301991200, 21703740051934476300, 520437222249938431200

Offset

0,2

Comments

The initial terms coincide with those of A170744, 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 (23,23,23,-276).

Formula

G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(276*t^4 - 23*t^3 - 23*t^2 - 23*t + 1).

Mathematica

CoefficientList[Series[(t^4 + 2 t^3 + 2 t^2 + 2 t + 1)/(276 t^4 - 23 t^3 - 23 t^2 - 23 t + 1), {t, 0, 20}], t] (* Jinyuan Wang, Mar 23 2020 *)
coxG[{4, 276, -23}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Aug 16 2023 *)

Crossrefs

Sequence in context: A159661 A104643 A162811 * A163525 A163993 A164638

Adjacent sequences: A163172 A163173 A163174 * A163176 A163177 A163178

Keyword

nonn

Author

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

Status

approved