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A163745
Number of reduced words of length n in Coxeter group on 43 generators S_i with relations (S_i)^2 = (S_i S_j)^5 = I.
1
1, 43, 1806, 75852, 3185784, 133802025, 5619647124, 236023587219, 9912923799660, 416339991317124, 17486161688852682, 734413837213650321, 30845173108213815708, 1295488532304021561975, 54410151353124129064362
OFFSET
0,2
COMMENTS
The initial terms coincide with those of A170762, although the two sequences are eventually different.
Computed with Magma using commands similar to those used to compute A154638.
FORMULA
G.f.: (t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(861*t^5 - 41*t^4 - 41*t^3 - 41*t^2 - 41*t + 1).
a(n) = 41*a(n-1)+41*a(n-2)+41*a(n-3)+41*a(n-4)-861*a(n-5). - Wesley Ivan Hurt, May 11 2021
MAPLE
seq(coeff(series((1+t)*(1-t^5)/(1-42*t+902*t^5-861*t^6), t, n+1), t, n), n = 0 .. 20); # G. C. Greubel, Aug 09 2019
MATHEMATICA
CoefficientList[Series[(1+t)*(1-t^5)/(1-42*t+902*t^5-861*t^6), {t, 0, 20}], t] (* G. C. Greubel, Aug 02 2017 *)
coxG[{5, 865, -41}] (* The coxG program is at A169452 *) (* G. C. Greubel, Aug 09 2019 *)
PROG
(PARI) my(t='t+O('t^20)); Vec((1+t)*(1-t^5)/(1-42*t+902*t^5-861*t^6)) \\ G. C. Greubel, Aug 02 2017
(Magma) R<t>:=PowerSeriesRing(Integers(), 20); Coefficients(R!( (1+t)*(1-t^5)/(1-42*t+902*t^5-861*t^6) )); // G. C. Greubel, Aug 09 2019
(SageMath)
def A163745_list(prec):
P.<t> = PowerSeriesRing(ZZ, prec)
return P((1+t)*(1-t^5)/(1-42*t+902*t^5-861*t^6)).list()
A163745_list(20) # G. C. Greubel, Aug 09 2019
CROSSREFS
Sequence in context: A198206 A162881 A163226 * A164113 A164687 A165175
KEYWORD
nonn
AUTHOR
John Cannon and N. J. A. Sloane, Dec 03 2009
STATUS
approved