A162937 - OEIS

A162937

Number of reduced words of length n in Coxeter group on 6 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.

1, 6, 30, 150, 735, 3600, 17640, 86400, 423210, 2073000, 10154040, 49737000, 243624060, 1193330400, 5845225440, 28631349600, 140243381160, 686946520800, 3364832751840, 16481777119200, 80731791755760, 395444141299200

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OFFSET

0,2

COMMENTS

The initial terms coincide with those of A003948, 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..21.

Index entries for linear recurrences with constant coefficients, signature (4, 4, 4, -10).

FORMULA

G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(10*t^4 - 4*t^3 - 4*t^2 - 4*t + 1)

CROSSREFS

Sequence in context: A157519 A075886 A001412 * A006818 A006819 A163317

Adjacent sequences: A162934 A162935 A162936 * A162938 A162939 A162940

KEYWORD

nonn

AUTHOR

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

STATUS

approved