A162830 Number of reduced words of length n in Coxeter group on 28 generators S_i with relations (S_i)^2 = (S_i S_j)^3 = I.

1, 28, 756, 20034, 530712, 14054040, 372171618, 9855587196, 260988761124, 6911320818402, 183020737961880, 4846626473132808, 128344953881202786, 3398740810188105564, 90003063973732401492, 2383397845569631005570

Offset

0,2

Comments

The initial terms coincide with those of A170747, 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 (26, 26, -351).

Formula

G.f.: (t^3 + 2*t^2 + 2*t + 1)/(351*t^3 - 26*t^2 - 26*t + 1)

Crossrefs

Sequence in context: A277060 A229463 A097834 * A163187 A163548 A164025

Adjacent sequences: A162827 A162828 A162829 * A162831 A162832 A162833

Keyword

nonn

Author

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

Status

approved