

A162805


Number of reduced words of length n in Coxeter group on 19 generators S_i with relations (S_i)^2 = (S_i S_j)^3 = I.


0



1, 19, 342, 5985, 104652, 1828503, 31947930, 558187605, 9752543136, 170394389307, 2977095147966, 52015183033833, 908798387526612, 15878335141888767, 277422946995884994, 4847075643050582301
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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, 153).


FORMULA

G.f.: (t^3 + 2*t^2 + 2*t + 1)/(153*t^3  17*t^2  17*t + 1)


MATHEMATICA

CoefficientList[Series[(t^3+2*t^2+2*t+1)/(153*t^317*t^217*t+1), {t, 0, 30}], t] (* Harvey P. Dale, Aug 14 2011 *)


CROSSREFS

Sequence in context: A202043 A142549 A049629 * A049664 A163110 A163453
Adjacent sequences: A162802 A162803 A162804 * A162806 A162807 A162808


KEYWORD

nonn


AUTHOR

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


STATUS

approved



