A162767 Number of reduced words of length n in Coxeter group on 12 generators S_i with relations (S_i)^2 = (S_i S_j)^3 = I.

1, 12, 132, 1386, 14520, 151800, 1586970, 16589100, 173411700, 1812724650, 18948963000, 198079233000, 2070582104250, 21644420407500, 226255667302500, 2365118861366250, 24723302164275000, 258440148554775000

Offset

0,2

Comments

The initial terms coincide with those of A003954, 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..17.

Index entries for linear recurrences with constant coefficients, signature (10, 10, -55).

Formula

G.f.: (t^3 + 2*t^2 + 2*t + 1)/(55*t^3 - 10*t^2 - 10*t + 1)

Crossrefs

Sequence in context: A119237 A038729 A125447 * A003495 A324947 A165150

Adjacent sequences: A162764 A162765 A162766 * A162768 A162769 A162770

Keyword

nonn

Author

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

Status

approved