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A162960 Number of reduced words of length n in Coxeter group on 9 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I. 0
1, 9, 72, 576, 4572, 36288, 288036, 2286144, 18145260, 144020016, 1143094932, 9072809424, 72011403324, 571558593312, 4536492984324, 36006402202848, 285784857170316, 2268290625889680, 18003551393278836, 142895208872692080 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The initial terms coincide with those of A003951, 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 (7, 7, 7, -28).

FORMULA

G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(28*t^4 - 7*t^3 - 7*t^2 - 7*t + 1)

CROSSREFS

Sequence in context: A076765 A006634 A129328 * A163391 A163953 A164375

Adjacent sequences:  A162957 A162958 A162959 * A162961 A162962 A162963

KEYWORD

nonn

AUTHOR

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

STATUS

approved

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Last modified September 20 12:43 EDT 2019. Contains 327238 sequences. (Running on oeis4.)