A164963 - OEIS

A164963

Number of reduced words of length n in Coxeter group on 25 generators S_i with relations (S_i)^2 = (S_i S_j)^8 = I.

1, 25, 600, 14400, 345600, 8294400, 199065600, 4777574400, 114661785300, 2751882840000, 66045187987500, 1585084507560000, 38042028082080000, 913008671585280000, 21912208060815360000, 525892992086016000000

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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.

LINKS

Table of n, a(n) for n=0..15.

Index entries for linear recurrences with constant coefficients, signature (23, 23, 23, 23, 23, 23, 23, -276).

FORMULA

G.f. (t^8 + 2*t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(276*t^8 -

23*t^7 - 23*t^6 - 23*t^5 - 23*t^4 - 23*t^3 - 23*t^2 - 23*t + 1)

MATHEMATICA

coxG[{8, 276, -23}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Feb 13 2017 *)

CROSSREFS

Sequence in context: A163525 A163993 A164638 * A165368 A165967 A166419

Adjacent sequences: A164960 A164961 A164962 * A164964 A164965 A164966

KEYWORD

nonn

AUTHOR

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

STATUS

approved