A162791 Number of reduced words of length n in Coxeter group on 16 generators S_i with relations (S_i)^2 = (S_i S_j)^3 = I.

1, 16, 240, 3480, 50400, 729120, 10547880, 152586000, 2207316720, 31931110680, 461916453600, 6682097644320, 96663430749480, 1398336169885200, 20228374156231920, 292624284336944280, 4233111921066520800

Offset

0,2

Comments

The initial terms coincide with those of A170735, 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..16.

Index entries for linear recurrences with constant coefficients, signature (14, 14, -105).

Formula

G.f.: (t^3 + 2*t^2 + 2*t + 1)/(105*t^3 - 14*t^2 - 14*t + 1)

Mathematica

CoefficientList[Series[(t^3+2t^2+2t+1)/(105t^3-14t^2-14t+1), {t, 0, 30}], t] (* Harvey P. Dale, Oct 02 2011 *)

Crossrefs

Sequence in context: A389269 A227440 A103975 * A060198 A097829 A010559

Adjacent sequences: A162788 A162789 A162790 * A162792 A162793 A162794

Keyword

nonn

Author

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

Status

approved