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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
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.
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
KEYWORD
nonn
AUTHOR
John Cannon and N. J. A. Sloane, Dec 03 2009
STATUS
approved