A164639 Number of reduced words of length n in Coxeter group on 26 generators S_i with relations (S_i)^2 = (S_i S_j)^7 = I.

1, 26, 650, 16250, 406250, 10156250, 253906250, 6347655925, 158691390000, 3967284547200, 99182108610000, 2479552588500000, 61988811543750000, 1549720209375000000, 38743003253906355300, 968575031835945300000

Offset: 0

Author

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

Keywords

• nonn

Comments

The initial terms coincide with those of A170745, 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 (24,24,24,24,24,24,-300).

Programs

Mathematica

coxG[{7,300,-24}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Feb 04 2015 *)

Formula

G.f.: (t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(300*t^7 - 24*t^6 - 24*t^5 - 24*t^4 - 24*t^3 - 24*t^2 - 24*t + 1).