A162768 Number of reduced words of length n in Coxeter group on 13 generators S_i with relations (S_i)^2 = (S_i S_j)^3 = I.

1, 13, 156, 1794, 20592, 235950, 2703558, 30975516, 354897114, 4066164102, 46587289320, 533764778118, 6115505911086, 70067216486124, 802781471013522, 9197712172364430, 105380993789073288, 1207382188488922446

Offset: 0

Author

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

Keywords

• nonn

Comments

The initial terms coincide with those of A170732, 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 (11, 11, -66).

Formula

G.f.: (t^3 + 2*t^2 + 2*t + 1)/(66*t^3 - 11*t^2 - 11*t + 1)