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%I #9 Sep 08 2022 08:44:46
%S 1,-20,150,-400,-875,7396,-7770,-36600,56510,154660,-872,-1314200,
%T -455605,6284960,3781830,-9954864,-43558410,-16664680,165132890,
%U 229738040,57372644,-1326447180,-2095012310,1723402120,7805180205
%N Expansion of Product_{m>=1} (1-m*q^m)^20.
%H G. C. Greubel, <a href="/A022680/b022680.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 18 2018 *)
%o (PARI) m=50; q='q+O('q^m); Vec(prod(n=1,m,(1-n*q^n)^20)) \\ _G. C. Greubel_, Jul 18 2018
%o (Magma) Coefficients(&*[(1-m*x^m)^20:m in [1..40]])[1..40] where x is PolynomialRing(Integers()).1; // _G. C. Greubel_, Jul 18 2018
%K sign
%O 0,2
%A _N. J. A. Sloane_
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