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A165215
Number of reduced words of length n in Coxeter group on 8 generators S_i with relations (S_i)^2 = (S_i S_j)^9 = I.
0
1, 8, 56, 392, 2744, 19208, 134456, 941192, 6588344, 46118380, 322828464, 2259797904, 15818575920, 110729965584, 775109298096, 5425761859728, 37980310429488, 265862014886160, 1861032997362084, 13027223233652040
OFFSET
0,2
COMMENTS
The initial terms coincide with those of A003950, although the two sequences are eventually different.
Computed with MAGMA using commands similar to those used to compute A154638.
FORMULA
G.f. (t^9 + 2*t^8 + 2*t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t +
1)/(21*t^9 - 6*t^8 - 6*t^7 - 6*t^6 - 6*t^5 - 6*t^4 - 6*t^3 - 6*t^2 - 6*t
+ 1)
CROSSREFS
Sequence in context: A163924 A164373 A164769 * A165786 A166366 A166538
KEYWORD
nonn
AUTHOR
John Cannon and N. J. A. Sloane, Dec 03 2009
STATUS
approved