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A164635
Number of reduced words of length n in Coxeter group on 22 generators S_i with relations (S_i)^2 = (S_i S_j)^7 = I.
0
1, 22, 462, 9702, 203742, 4278582, 89850222, 1886854431, 39623938200, 832102600560, 17474152477320, 366957157200480, 7706099359922040, 161828066791314000, 3398388987509621490, 71366160020435695800
OFFSET
0,2
COMMENTS
The initial terms coincide with those of A170741, although the two sequences are eventually different.
Computed with MAGMA using commands similar to those used to compute A154638.
FORMULA
G.f.: (t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(210*t^7 - 20*t^6 - 20*t^5 - 20*t^4 - 20*t^3 - 20*t^2 - 20*t + 1).
a(n) = -210*a(n-7) + 20*Sum_{k=1..6} a(n-k). - Wesley Ivan Hurt, May 05 2021
MATHEMATICA
coxG[{7, 210, -20}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Feb 11 2015 *)
CROSSREFS
Sequence in context: A163149 A163514 A163988 * A164956 A165364 A165895
KEYWORD
nonn
AUTHOR
John Cannon and N. J. A. Sloane, Dec 03 2009
STATUS
approved