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%I #19 Sep 08 2022 08:44:46
%S 1,4,18,64,219,676,2030,5736,15793,41864,108430,273240,675526,1634780,
%T 3891960,9108872,21018870,47815572,107446898,238524144,523812125,
%U 1138233100,2449710880,5223395480,11042278208
%N Expansion of Product_{m>=1} (1-m*q^m)^-4.
%C This sequence is obtained from the generalized Euler transform in A266964 by taking f(n) = 4, g(n) = n. - _Seiichi Manyama_, Dec 29 2017
%H Seiichi Manyama, <a href="/A022728/b022728.txt">Table of n, a(n) for n = 0..1000</a>
%F G.f.: exp(4*Sum_{j>=1} Sum_{k>=1} k^j*x^(j*k)/j). - _Ilya Gutkovskiy_, Feb 07 2018
%t With[{nmax = 50}, CoefficientList[Series[Product[(1 - k*q^k)^-4, {k, 1, nmax}], {q, 0, nmax}], q]] (* _G. C. Greubel_, Jul 25 2018 *)
%o (PARI) m=50; q='q+O('q^m); Vec(prod(n=1,m,(1-n*q^n)^-4)) \\ _G. C. Greubel_, Jul 25 2018
%o (Magma) n:=50; R<x>:=PowerSeriesRing(Integers(), n); Coefficients(R!(&*[(1/(1-m*x^m))^4:m in [1..n]])); // _G. C. Greubel_, Jul 25 2018
%Y Column k=4 of A297328.
%K nonn
%O 0,2
%A _N. J. A. Sloane_
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