A165365 Number of reduced words of length n in Coxeter group on 23 generators S_i with relations (S_i)^2 = (S_i S_j)^9 = I.

1, 23, 506, 11132, 244904, 5387888, 118533536, 2607737792, 57370231424, 1262145091075, 27767191998084, 610878223835649, 13439320921695900, 295665060218165484, 6504631323498465696, 143101889088340396368

Offset

0,2

Comments

The initial terms coincide with those of A170742, 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..15.

Index entries for linear recurrences with constant coefficients, signature (21, 21, 21, 21, 21, 21, 21, 21, -231).

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)/(231*t^9 - 21*t^8 - 21*t^7 - 21*t^6 - 21*t^5 - 21*t^4 - 21*t^3 -

21*t^2 - 21*t + 1)

Crossrefs

Sequence in context: A163991 A164636 A164957 * A165939 A166417 A166610

Adjacent sequences: A165362 A165363 A165364 * A165366 A165367 A165368

Keyword

nonn

Author

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

Status

approved