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A165215 Number of reduced words of length n in Coxeter group on 8 generators S_i with relations (S_i)^2 = (S_i S_j)^9 = I. 0
1, 8, 56, 392, 2744, 19208, 134456, 941192, 6588344, 46118380, 322828464, 2259797904, 15818575920, 110729965584, 775109298096, 5425761859728, 37980310429488, 265862014886160, 1861032997362084, 13027223233652040 (list; graph; refs; listen; history; text; internal format)
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, 6, 6, 6, 6, 6, 6, -21).

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)/(21*t^9 - 6*t^8 - 6*t^7 - 6*t^6 - 6*t^5 - 6*t^4 - 6*t^3 - 6*t^2 - 6*t

+ 1)

CROSSREFS

Sequence in context: A163924 A164373 A164769 * A165786 A166366 A166538

Adjacent sequences:  A165212 A165213 A165214 * A165216 A165217 A165218

KEYWORD

nonn

AUTHOR

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

STATUS

approved

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Last modified November 19 08:43 EST 2019. Contains 329318 sequences. (Running on oeis4.)