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Revision History for A162378

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Showing entries 1-10 | older changes
Number of reduced words of length n in the Weyl group D_31.
(history; published version)
#13 by Ray Chandler at Wed Feb 21 11:37:49 EST 2024
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editing

approved

#12 by Ray Chandler at Wed Feb 21 11:37:46 EST 2024
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approved

editing

#11 by Alois P. Heinz at Wed Feb 15 11:08:08 EST 2023
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editing

approved

#10 by Alois P. Heinz at Wed Feb 15 11:08:05 EST 2023
FORMULA

The growth series for D_k is the polynomial f(k)*Prod_Product_{i=1..k-1} f(2*i), where f(m) = (1-x^m)/(1-x) [Corrected by N. J. A. Sloane, Aug 07 2021]. This is a row of the triangle in A162206.

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proposed

editing

#9 by Jean-François Alcover at Wed Feb 15 08:07:43 EST 2023
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editing

proposed

#8 by Jean-François Alcover at Wed Feb 15 08:07:37 EST 2023
MATHEMATICA

f[m_] := (1-x^m)/(1-x);

With[{k = 31}, CoefficientList[f[k]*Product[f[2i], {i, 1, k-1}] + O[x]^(k-10), x]] (* Jean-François Alcover, Feb 15 2023, after Maple code *)

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approved

editing

#7 by N. J. A. Sloane at Sat Aug 07 13:57:30 EDT 2021
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editing

approved

#6 by N. J. A. Sloane at Sat Aug 07 13:57:28 EDT 2021
COMMENTS

Computed with MAGMA using commands similar to those used to compute A161409.

LINKS

<a href="/index/Gre#GROWTH">Index entries for growth series for groups</a>

FORMULA

G.f. The growth series for D_m k is the polynomial f(nk) * Product( f(2i), Prod_{i=1..nk-1 )/ } f(12*i)^n, , where f(km) = (1-x^km)/(1-x) [Corrected by _N. J. A. Only finitely many terms are nonzeroSloane_, Aug 07 2021]. This is a row of the triangle in A162206.

MAPLE

# Growth series for D_k, truncated to terms of order M. - N. J. A. Sloane, Aug 07 2021

f := proc(m::integer) (1-x^m)/(1-x) ; end proc:

g := proc(k, M) local a, i; global f;

a:=f(k)*mul(f(2*i), i=1..k-1);

seriestolist(series(a, x, M+1));

end proc;

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approved

editing

#5 by Jon E. Schoenfield at Sun Jul 19 11:06:29 EDT 2015
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editing

approved

#4 by Jon E. Schoenfield at Sun Jul 19 11:06:28 EDT 2015
REFERENCES

J. E. Humphreys, Reflection Groups and Coxeter Groups, Cambridge, 1990. See under Poincare Poincaré polynomial.

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approved

editing