A164992 Number of reduced words of length n in Coxeter group on 31 generators S_i with relations (S_i)^2 = (S_i S_j)^8 = I.

1, 31, 930, 27900, 837000, 25110000, 753300000, 22599000000, 677969999535, 20339099972100, 610172998744965, 18305189949807900, 549155698118005500, 16474670932253220000, 494240127628988250000, 14827203818711397000000

Offset

0,2

Comments

The initial terms coincide with those of A170750, 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 (29, 29, 29, 29, 29, 29, 29, -435).

Formula

G.f. (t^8 + 2*t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(435*t^8 -

29*t^7 - 29*t^6 - 29*t^5 - 29*t^4 - 29*t^3 - 29*t^2 - 29*t + 1)

Crossrefs

Sequence in context: A163564 A164030 A164667 * A165547 A166075 A166425

Adjacent sequences: A164989 A164990 A164991 * A164993 A164994 A164995

Keyword

nonn

Author

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

Status

approved