A165321 Number of reduced words of length n in Coxeter group on 17 generators S_i with relations (S_i)^2 = (S_i S_j)^9 = I.

1, 17, 272, 4352, 69632, 1114112, 17825792, 285212672, 4563402752, 73014443896, 1168231100160, 18691697567880, 299067160531200, 4785074559621120, 76561192811888640, 1224979082717429760, 19599665287114260480

Offset

0,2

Comments

The initial terms coincide with those of A170736, 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..16.

Index entries for linear recurrences with constant coefficients, signature (15, 15, 15, 15, 15, 15, 15, 15, -120).

Formula

G.f. (t^9 + 2*t^8 + 2*t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t +

1)/(120*t^9 - 15*t^8 - 15*t^7 - 15*t^6 - 15*t^5 - 15*t^4 - 15*t^3 -

15*t^2 - 15*t + 1)

Mathematica

coxG[{9, 120, -15}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Jan 31 2021 *)

Crossrefs

Sequence in context: A163965 A164628 A164868 * A165879 A166411 A166585

Adjacent sequences: A165318 A165319 A165320 * A165322 A165323 A165324

Keyword

nonn

Author

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

Status

approved