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A164638
Number of reduced words of length n in Coxeter group on 25 generators S_i with relations (S_i)^2 = (S_i S_j)^7 = I.
0
1, 25, 600, 14400, 345600, 8294400, 199065600, 4777574100, 114661771200, 2751882336300, 66045171931200, 1585084026988800, 38042014263091200, 913008285082828800, 21912197468435340900, 525892706277189044400
OFFSET
0,2
COMMENTS
The initial terms coincide with those of A170744, 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)/(276*t^7 - 23*t^6 - 23*t^5 - 23*t^4 - 23*t^3 - 23*t^2 - 23*t + 1).
MATHEMATICA
coxG[{7, 276, -23}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Dec 05 2014 *)
CROSSREFS
Sequence in context: A163175 A163525 A163993 * A164963 A165368 A165967
KEYWORD
nonn,easy
AUTHOR
John Cannon and N. J. A. Sloane, Dec 03 2009
STATUS
approved