

A163187


Number of reduced words of length n in Coxeter group on 28 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.


0



1, 28, 756, 20412, 550746, 14859936, 400943088, 10818033408, 291886435386, 7875524871396, 212493231821052, 5733379591597476, 154695004916717538, 4173898512013677720, 112617914185202621832, 3038596784018807730264
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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 (26,26,26,351).


FORMULA

G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(351*t^4  26*t^3  26*t^2  26*t + 1).


MATHEMATICA

coxG[{4, 351, 26}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Jul 05 2017 *)


PROG

(PARI) Vec((t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(351*t^4  26*t^3  26*t^2  26*t + 1) + O(t^20)) \\ Jinyuan Wang, Mar 23 2020


CROSSREFS

Sequence in context: A229463 A097834 A162830 * A163548 A164025 A164664
Adjacent sequences: A163184 A163185 A163186 * A163188 A163189 A163190


KEYWORD

nonn


AUTHOR

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


STATUS

approved



