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A164706 Number of reduced words of length n in Coxeter group on 5 generators S_i with relations (S_i)^2 = (S_i S_j)^8 = I. 0
1, 5, 20, 80, 320, 1280, 5120, 20480, 81910, 327600, 1310250, 5240400, 20959200, 83827200, 335270400, 1340928000, 5363097690, 21449933820, 85789908630, 343120332420, 1372324139280, 5488667867520, 21952156999680, 87798571269120 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The initial terms coincide with those of A003947, 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..23.

Index entries for linear recurrences with constant coefficients, signature (3, 3, 3, 3, 3, 3, 3, -6).

FORMULA

G.f. (t^8 + 2*t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(6*t^8 -

3*t^7 - 3*t^6 - 3*t^5 - 3*t^4 - 3*t^3 - 3*t^2 - 3*t + 1)

CROSSREFS

Sequence in context: A163316 A163878 A164354 * A165185 A165757 A166331

Adjacent sequences:  A164703 A164704 A164705 * A164707 A164708 A164709

KEYWORD

nonn

AUTHOR

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

STATUS

approved

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Last modified December 6 04:17 EST 2021. Contains 349562 sequences. (Running on oeis4.)