A164690 Number of reduced words of length n in Coxeter group on 45 generators S_i with relations (S_i)^2 = (S_i S_j)^7 = I.

1, 45, 1980, 87120, 3833280, 168664320, 7421230080, 326534122530, 14367501347760, 632170057385790, 27815482440686160, 1223881223681492640, 53850773678802946560, 2369434034687289546240, 104255097210318976508070

Offset

0,2

Comments

The initial terms coincide with those of A170764, 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..14.

Index entries for linear recurrences with constant coefficients, signature (43, 43, 43, 43, 43, 43, -946).

Formula

G.f.: (t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(946*t^7 - 43*t^6 - 43*t^5 - 43*t^4 - 43*t^3 - 43*t^2 - 43*t + 1).

Crossrefs

Sequence in context: A163231 A163749 A164330 * A165177 A165699 A166258

Adjacent sequences: A164687 A164688 A164689 * A164691 A164692 A164693

Keyword

nonn

Author

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

Status

approved