A164638 Number of reduced words of length n in Coxeter group on 25 generators S_i with relations (S_i)^2 = (S_i S_j)^7 = I.

1, 25, 600, 14400, 345600, 8294400, 199065600, 4777574100, 114661771200, 2751882336300, 66045171931200, 1585084026988800, 38042014263091200, 913008285082828800, 21912197468435340900, 525892706277189044400

Offset: 0

Author

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

Keywords

• nonn
• easy

Comments

The initial terms coincide with those of A170744, 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 (23, 23, 23, 23, 23, 23, -276).

Programs

Mathematica

coxG[{7,276,-23}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Dec 05 2014 *)

Formula

G.f.: (t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(276*t^7 - 23*t^6 - 23*t^5 - 23*t^4 - 23*t^3 - 23*t^2 - 23*t + 1).