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Expansion of Product_{m>=1} (1+m*q^m)^-21.
2

%I #9 Jul 20 2018 06:02:49

%S 1,-21,189,-952,3087,-8400,27503,-92907,246981,-588490,1649823,

%T -4645179,10989769,-25476717,65615424,-161705810,363998754,-834169539,

%U 1973130271,-4510112565,9969930495,-22054706773

%N Expansion of Product_{m>=1} (1+m*q^m)^-21.

%H G. C. Greubel, <a href="/A022713/b022713.txt">Table of n, a(n) for n = 0..1000</a>

%t With[{nmax = 50}, CoefficientList[Series[Product[(1 + k*q^k)^-21, {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)^-21)) \\ _G. C. Greubel_, Jul 20 2018

%K sign

%O 0,2

%A _N. J. A. Sloane_