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A163519 Number of reduced words of length n in Coxeter group on 24 generators S_i with relations (S_i)^2 = (S_i S_j)^5 = I. 1
1, 24, 552, 12696, 292008, 6715908, 154459536, 3552423600, 81702391056, 1879077904176, 43217018799372, 993950655137880, 22859927229943848, 525756756894338904, 12091909332851083560, 278102505382114851108 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The initial terms coincide with those of A170743, although the two sequences are eventually different.

Computed with MAGMA using commands similar to those used to compute A154638.

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..730

Index entries for linear recurrences with constant coefficients, signature (22, 22, 22, 22, -253).

FORMULA

G.f.: (t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(253*t^5 - 22*t^4 - 22*t^3 - 22*t^2 - 22*t + 1).

MATHEMATICA

CoefficientList[Series[(1+x)*(1-x^5)/(1-23*x+275*x^5-253*x^6), {x, 0, 20}], x] (* G. C. Greubel, Jul 27 2017 *)

coxG[{5, 253, -22}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Aug 16 2018 *)

PROG

(PARI) my(x='x+O('x^20)); Vec((1+x)*(1-x^5)/(1-23*x+275*x^5-253*x^6)) \\ G. C. Greubel, Jul 27 2017

(MAGMA) R<x>:=PowerSeriesRing(Integers(), 20); Coefficients(R!( (1+x)*(1-x^5)/(1-23*x+275*x^5-253*x^6) )); // G. C. Greubel, May 16 2019

(Sage) ((1+x)*(1-x^5)/(1-23*x+275*x^5-253*x^6)).series(x, 20).coefficients(x, sparse=False) # G. C. Greubel, May 16 2019

CROSSREFS

Sequence in context: A162810 A010561 A163174 * A163992 A164637 A164959

Adjacent sequences:  A163516 A163517 A163518 * A163520 A163521 A163522

KEYWORD

nonn,easy

AUTHOR

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

STATUS

approved

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Last modified August 22 16:37 EDT 2019. Contains 326179 sequences. (Running on oeis4.)