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A165693 Number of reduced words of length n in Coxeter group on 42 generators S_i with relations (S_i)^2 = (S_i S_j)^9 = I. 0
1, 42, 1722, 70602, 2894682, 118681962, 4865960442, 199504378122, 8179679503002, 335366859622221, 13750041244475760, 563751691022059680, 23113819331845141200, 947666592603219256320, 38854330296632296661040 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The initial terms coincide with those of A170761, 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..14.

Index entries for linear recurrences with constant coefficients, signature (40, 40, 40, 40, 40, 40, 40, 40, -820).

FORMULA

G.f. (t^9 + 2*t^8 + 2*t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t +

1)/(820*t^9 - 40*t^8 - 40*t^7 - 40*t^6 - 40*t^5 - 40*t^4 - 40*t^3 -

40*t^2 - 40*t + 1)

MATHEMATICA

coxG[{9, 820, -40}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Nov 05 2017 *)

CROSSREFS

Sequence in context: A164112 A164686 A165174 * A166230 A166436 A166716

Adjacent sequences:  A165690 A165691 A165692 * A165694 A165695 A165696

KEYWORD

nonn

AUTHOR

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

STATUS

approved

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Last modified July 27 18:27 EDT 2021. Contains 346308 sequences. (Running on oeis4.)