A162754 Number of reduced words of length n in Coxeter group on 8 generators S_i with relations (S_i)^2 = (S_i S_j)^3 = I.

1, 8, 56, 364, 2352, 15120, 97188, 624456, 4012344, 25779852, 165639600, 1064257488, 6838005636, 43935147144, 282289509432, 1813749821100, 11653597893168, 74876006587536, 481088880641124, 3091063767615432

Offset

0,2

Comments

The initial terms coincide with those of A003950, 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..19.

Index entries for linear recurrences with constant coefficients, signature (6, 6, -21).

Formula

G.f.: (t^3 + 2*t^2 + 2*t + 1)/(21*t^3 - 6*t^2 - 6*t + 1)

Crossrefs

Sequence in context: A307813 A291387 A272773 * A081626 A272763 A199939

Adjacent sequences: A162751 A162752 A162753 * A162755 A162756 A162757

Keyword

nonn

Author

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

Status

approved