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Expansion of Product_{m>=1} (1+m*q^m)^-20.
2

%I #9 Jul 20 2018 06:04:32

%S 1,-20,170,-800,2415,-6404,21550,-71080,178295,-419200,1203282,

%T -3294360,7476320,-17381780,44919500,-107605880,237628435,-544086720,

%U 1273805460,-2864694880,6256648862,-13710129840

%N Expansion of Product_{m>=1} (1+m*q^m)^-20.

%H G. C. Greubel, <a href="/A022712/b022712.txt">Table of n, a(n) for n = 0..1000</a>

%t With[{nmax = 50}, CoefficientList[Series[Product[(1 + k*q^k)^-20, {k, 1, nmax}], {q, 0, nmax}], q]] (* _G. C. Greubel_, Jul 20 2018 *)

%o (PARI) m=50; q='q+O('q^m); Vec(prod(n=1,m,(1+n*q^n)^-20)) \\ _G. C. Greubel_, Jul 20 2018

%K sign

%O 0,2

%A _N. J. A. Sloane_