A167919 Number of reduced words of length n in Coxeter group on 13 generators S_i with relations (S_i)^2 = (S_i S_j)^16 = I.
1, 13, 156, 1872, 22464, 269568, 3234816, 38817792, 465813504, 5589762048, 67077144576, 804925734912, 9659108818944, 115909305827328, 1390911669927936, 16690940039135232, 200291280469622706
Offset: 0
Keywords
Links
- G. C. Greubel, Table of n, a(n) for n = 0..500
- Index entries for linear recurrences with constant coefficients, signature (11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,-66).
Crossrefs
Programs
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Magma
R
:=PowerSeriesRing(Integers(), 40); Coefficients(R!( (1+x)*(1-x^16)/(1-12*x+77*x^16-66*x^17) )); // G. C. Greubel, Sep 13 2023 -
Mathematica
CoefficientList[Series[(1+t)*(1-t^16)/(1-12*t+77*t^16-66*t^17), {t, 0, 50}], t] (* G. C. Greubel, Jul 01 2016; Sep 13 2023 *) coxG[{16,66,-11}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Mar 28 2018 *)
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SageMath
def A167919_list(prec): P.
= PowerSeriesRing(ZZ, prec) return P( (1+x)*(1-x^16)/(1-12*x+77*x^16-66*x^17) ).list() A167919_list(40) # G. C. Greubel, Sep 13 2023
Formula
G.f.: (t^16 + 2*t^15 + 2*t^14 + 2*t^13 + 2*t^12 + 2*t^11 + 2*t^10 + 2*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^16 - 11*t^15 - 11*t^14 - 11*t^13 - 11*t^12 - 11*t^11 - 11*t^10 - 11*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).
From G. C. Greubel, Sep 13 2023: (Start)
G.f.: (1+t)*(1-t^16)/(1 - 12*t + 77*t^16 - 66*t^17).
a(n) = 11*Sum_{j=1..15} a(n-j) - 66*a(n-16). (End)
Comments