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Expansion of Product_{k>=1} (1 + x^(3*k))^(3*k) / (1 + x^k)^k.
2

%I #12 Apr 24 2017 08:32:00

%S 1,-1,-1,1,-2,-3,7,-4,-1,20,-9,-15,45,-39,-38,95,-81,-99,244,-196,

%T -188,538,-371,-421,1256,-823,-820,2575,-1672,-1904,5367,-3714,-3861,

%U 10555,-7362,-8159,21391,-14975,-15592,41654,-28293,-30748,82026,-54899,-57331,155933

%N Expansion of Product_{k>=1} (1 + x^(3*k))^(3*k) / (1 + x^k)^k.

%H Seiichi Manyama, <a href="/A285294/b285294.txt">Table of n, a(n) for n = 0..10000</a>

%t nmax = 50; CoefficientList[Series[Product[(1 + x^(3*k))^(3*k) / (1 + x^k)^k, {k,1,nmax}], {x,0,nmax}], x] (* _Vaclav Kotesovec_, Apr 16 2017 *)

%Y Product_{k>=1} (1 + x^(m*k))^(m*k) / (1 + x^k)^k: A284628 (m=2), this sequence (m=3), A285295 (m=4).

%Y Cf. A262924.

%K sign

%O 0,5

%A _Seiichi Manyama_, Apr 16 2017