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

Offset: 0

Author

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

Keywords

• nonn

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

• 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)