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Expansion of Product_{k>=1} ((1 + x^(4*k)) / (1 - x^k)).
1

%I #6 Apr 19 2017 11:56:26

%S 1,1,2,3,6,8,13,18,28,38,55,74,106,140,192,253,342,444,588,758,992,

%T 1267,1634,2072,2650,3334,4218,5276,6627,8234,10262,12682,15708,19308,

%U 23764,29070,35597,43340,52792,64008,77622,93724,113160,136124,163712,196225

%N Expansion of Product_{k>=1} ((1 + x^(4*k)) / (1 - x^k)).

%F a(n) ~ sqrt(3) * exp(sqrt(3*n)*Pi/2) / (16*n).

%t nmax = 50; CoefficientList[Series[Product[((1+x^(4*k))/(1-x^k)), {k, 1, nmax}], {x, 0, nmax}], x]

%Y Cf. A006950, A015128, A279328, A266648, A285460.

%K nonn

%O 0,3

%A _Vaclav Kotesovec_, Apr 19 2017