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A163207 Number of reduced words of length n in Coxeter group on 29 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I. 1
1, 29, 812, 22736, 636202, 17802288, 498146166, 13939191504, 390048294510, 10914382803996, 305407698579522, 8545958486918244, 239134137088822794, 6691482951706744632, 187241958166564053774, 5239429159586654676168 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The initial terms coincide with those of A170748, although the two sequences are eventually different.

Computed with MAGMA using commands similar to those used to compute A154638.

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..685

Index entries for linear recurrences with constant coefficients, signature (27, 27, 27, -378).

FORMULA

G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(378*t^4 - 27*t^3 - 27*t^2 - 27*t + 1).

MATHEMATICA

CoefficientList[Series[(t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(378*t^4 - 27*t^3 - 27*t^2 - 27*t + 1), {t, 0, 100}], t] (* or *) LinearRecurrence[{27, 27, 27, -378}, {1, 29, 812, 22736}, 50] (* G. C. Greubel, Dec 10 2016 *)

PROG

(PARI) Vec((t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(378*t^4 - 27*t^3 - 27*t^2 - 27*t + 1) + O(t^50)) \\ G. C. Greubel, Dec 10 2016

CROSSREFS

Sequence in context: A180844 A159669 A162831 * A163549 A164026 A164665

Adjacent sequences:  A163204 A163205 A163206 * A163208 A163209 A163210

KEYWORD

nonn,easy

AUTHOR

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

STATUS

approved

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Last modified January 22 11:56 EST 2019. Contains 319363 sequences. (Running on oeis4.)