A162809 - OEIS

A162809

Number of reduced words of length n in Coxeter group on 23 generators S_i with relations (S_i)^2 = (S_i S_j)^3 = I.

1, 23, 506, 10879, 233772, 5020785, 107832648, 2315920761, 49739020254, 1068244419627, 22942674541710, 492739584509403, 10582562979139536, 227281596017492709, 4881324494907605052, 104836155861245820165

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OFFSET

0,2

COMMENTS

The initial terms coincide with those of A170742, 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 (21, 21, -231).

FORMULA

G.f.: (t^3 + 2*t^2 + 2*t + 1)/(231*t^3 - 21*t^2 - 21*t + 1)

CROSSREFS

Sequence in context: A218715 A133283 A121903 * A212336 A163171 A163518

Adjacent sequences: A162806 A162807 A162808 * A162810 A162811 A162812

KEYWORD

nonn

AUTHOR

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

STATUS

approved