A165341 Number of reduced words of length n in Coxeter group on 19 generators S_i with relations (S_i)^2 = (S_i S_j)^9 = I.

1, 19, 342, 6156, 110808, 1994544, 35901792, 646232256, 11632180608, 209379250773, 3768826510836, 67838877139815, 1221099787522476, 21979796157509076, 395636330513044512, 7121453943436661808

Offset

0,2

Comments

The initial terms coincide with those of A170738, 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 (17, 17, 17, 17, 17, 17, 17, 17, -153).

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)/(153*t^9 - 17*t^8 - 17*t^7 - 17*t^6 - 17*t^5 - 17*t^4 - 17*t^3 -

17*t^2 - 17*t + 1)

Crossrefs

Sequence in context: A163968 A164631 A164909 * A165881 A166413 A166600

Adjacent sequences: A165338 A165339 A165340 * A165342 A165343 A165344

Keyword

nonn

Author

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

Status

approved