A162803 - OEIS

A162803

Number of reduced words of length n in Coxeter group on 17 generators S_i with relations (S_i)^2 = (S_i S_j)^3 = I.

1, 17, 272, 4216, 65280, 1009800, 15620280, 241617600, 3737392200, 57810713400, 894227472000, 13832085717000, 213957412227000, 3309535172520000, 51192538485165000, 791856215398035000, 12248587087545600000

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OFFSET

0,2

COMMENTS

The initial terms coincide with those of A170736, 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 (15, 15, -120).

FORMULA

G.f.: (t^3 + 2*t^2 + 2*t + 1)/(120*t^3 - 15*t^2 - 15*t + 1)

MATHEMATICA

coxG[{3, 120, -15}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Aug 08 2017 *)

CROSSREFS

Sequence in context: A090380 A142898 A159678 * A097830 A163093 A163451

Adjacent sequences: A162800 A162801 A162802 * A162804 A162805 A162806

KEYWORD

nonn

AUTHOR

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

STATUS

approved

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