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%I #18 Jul 20 2018 04:21:19
%S 1,-4,2,0,27,-36,14,-104,209,-392,670,-728,2278,-4444,4808,-9800,
%T 21750,-35604,51906,-91120,176285,-290444,455168,-741336,1372544,
%U -2419348,3490310,-5765744,10788815,-17086420,26221946,-44374160
%N Expansion of Product_{m>=1} (1 + m*q^m)^-4.
%H Robert Israel, <a href="/A022696/b022696.txt">Table of n, a(n) for n = 0..3000</a>
%F G.f.: exp(-4*Sum_{j>=1} Sum_{k>=1} (-1)^(j+1)*k^j*x^(j*k)/j). - _Ilya Gutkovskiy_, Feb 08 2018
%p N:= 100: # to get a(0)..a(N)
%p P:= mul((1+m*q^m)^(-4),m=1..N):
%p S:=series(P,q,N+1):
%p [seq(coeff(S,q,j),j=0..N)]; # _Robert Israel_, Jan 23 2018
%t With[{nmax = 50}, CoefficientList[Series[Product[(1 + k*q^k)^-4, {k, 1, nmax}], {q, 0, nmax}], q]] (* _G. C. Greubel_, Jul 19 2018 *)
%o (PARI) m=50; q='q+O('q^m); Vec(prod(n=1,m,(1+n*q^n)^-4)) \\ _G. C. Greubel_, Jul 19 2018
%Y Column k=4 of A297325.
%K sign
%O 0,2
%A _N. J. A. Sloane_
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