A165269 - OEIS

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A165269

Number of reduced words of length n in Coxeter group on 13 generators S_i with relations (S_i)^2 = (S_i S_j)^9 = I.

1, 13, 156, 1872, 22464, 269568, 3234816, 38817792, 465813504, 5589761970, 67077142704, 804925701294, 9659108281680, 115909297773984, 1390911554013696, 16690938416875008, 200291258227027968

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OFFSET

0,2

COMMENTS

The initial terms coincide with those of A170732, 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..16.

Index entries for linear recurrences with constant coefficients, signature (11, 11, 11, 11, 11, 11, 11, 11, -66).

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)/(66*t^9 - 11*t^8 - 11*t^7 - 11*t^6 - 11*t^5 - 11*t^4 - 11*t^3 -

11*t^2 - 11*t + 1)

MATHEMATICA

coxG[{9, 66, -11}] (* The coxG program is at A169452 *) (* Harvey P. Dale, May 03 2022 *)

CROSSREFS

Sequence in context: A163958 A164610 A164815 * A165873 A166377 A166558

Adjacent sequences: A165266 A165267 A165268 * A165270 A165271 A165272

KEYWORD

nonn

AUTHOR

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

STATUS

approved