OFFSET
0,5
COMMENTS
The Molien series for the finite Coxeter group of type A_k (k >= 1) has g.f. = 1/Product_{i=2..k+1} (1 - x^i).
Note that this is the root system A_k, not the alternating group Alt_k.
REFERENCES
J. E. Humphreys, Reflection Groups and Coxeter Groups, Cambridge, 1990. See Table 3.1, page 59.
LINKS
Ray Chandler, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (0, 1, 1, 1, 0, 0, -1, -1, -1, -1, -1, 0, 0, -1, 0, 1, 2, 3, 3, 3, 2, 0, -1, -2, -3, -4, -4, -5, -4, -3, -1, 1, 3, 5, 7, 7, 6, 5, 3, 2, -1, -4, -6, -7, -8, -7, -6, -4, -1, 2, 3, 5, 6, 7, 7, 5, 3, 1, -1, -3, -4, -5, -4, -4, -3, -2, -1, 0, 2, 3, 3, 3, 2, 1, 0, -1, 0, 0, -1, -1, -1, -1, -1, 0, 0, 1, 1, 1, 0, -1).
FORMULA
G.f.: 1/((1-t^2)*(1-t^3)*(1-t^4)*(1-t^5)*(1-t^6)*(1-t^7)*(1-t^8)*(1-t^9)*(1-t^10)*(1-t^11)*(1-t^12)*(1-t^13)).
MAPLE
S:=series(1/mul(1-x^j, j=2..13)), x, 75):
seq(coeff(S, x, j), j=0..70); # G. C. Greubel, Feb 04 2020
MATHEMATICA
CoefficientList[Series[1/Product[1-x^j, {j, 2, 13}], {x, 0, 70}], x] (* G. C. Greubel, Feb 04 2020 *)
LinearRecurrence[{0, 1, 1, 1, 0, 0, -1, -1, -1, -1, -1, 0, 0, -1, 0, 1, 2, 3, 3, 3, 2, 0, -1, -2, -3, -4, -4, -5, -4, -3, -1, 1, 3, 5, 7, 7, 6, 5, 3, 2, -1, -4, -6, -7, -8, -7, -6, -4, -1, 2, 3, 5, 6, 7, 7, 5, 3, 1, -1, -3, -4, -5, -4, -4, -3, -2, -1, 0, 2, 3, 3, 3, 2, 1, 0, -1, 0, 0, -1, -1, -1, -1, -1, 0, 0, 1, 1, 1, 0, -1}, {1, 0, 1, 1, 2, 2, 4, 4, 7, 8, 12, 14, 21, 24, 33, 40, 53, 63, 83, 98, 126, 150, 188, 223, 278, 327, 401, 473, 573, 672, 809, 944, 1126, 1312, 1551, 1800, 2118, 2446, 2859, 3295, 3829, 4395, 5086, 5817, 6699, 7642, 8760, 9961, 11380, 12898, 14678, 16596, 18819, 21217, 23987, 26971, 30397, 34099, 38316, 42877, 48058, 53649, 59972, 66811, 74499, 82813, 92136, 102204, 113455, 125613, 139140, 153754, 169979, 187481, 206857, 227767, 250835, 275713, 303108, 332617, 365036, 399950, 438201, 479372, 524403, 572813, 625657, 682451, 744307, 810735}, 80] (* Harvey P. Dale, Jul 01 2021 *)
PROG
(PARI) Vec( 1/prod(j=2, 13, 1-x^j) +O('x^70) ) \\ G. C. Greubel, Feb 04 2020
(Magma) R<x>:=PowerSeriesRing(Integers(), 70); Coefficients(R!( 1/(&*[1-x^j: j in [2..13]]) )); // G. C. Greubel, Feb 04 2020
(Sage)
def A266781_list(prec):
P.<x> = PowerSeriesRing(ZZ, prec)
return P( 1/prod(1-x^j for j in (2..13)) ).list()
A266781_list(70) # G. C. Greubel, Feb 04 2020
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jan 11 2016
STATUS
approved