A165219 Number of reduced words of length n in Coxeter group on 10 generators S_i with relations (S_i)^2 = (S_i S_j)^9 = I.

1, 10, 90, 810, 7290, 65610, 590490, 5314410, 47829690, 430467165, 3874204080, 34867833120, 313810465680, 2824293899520, 25418642471280, 228767758621920, 2058909615020880, 18530184622000320, 166771644379316460

Offset

0,2

Comments

The initial terms coincide with those of A003952, 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..18.

Index entries for linear recurrences with constant coefficients, signature (8, 8, 8, 8, 8, 8, 8, 8, -36).

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)/(36*t^9 - 8*t^8 - 8*t^7 - 8*t^6 - 8*t^5 - 8*t^4 - 8*t^3 - 8*t^2 - 8*t

+ 1)

Crossrefs

Sequence in context: A163954 A164548 A164779 * A165788 A166368 A166543

Adjacent sequences: A165216 A165217 A165218 * A165220 A165221 A165222

Keyword

nonn

Author

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

Status

approved