Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #4 Aug 28 2015 05:06:57
%S 1,4,8,12,20,36,56,80,120,180,252,348,492,680,912,1228,1652,2180,2856,
%T 3744,4860,6256,8044,10284,13048,16520,20848,26140,32672,40756,50596,
%U 62576,77256,95060,116540,142592,174036,211736,257056,311448,376332,453764,546160
%N Expansion of Product_{k>=0} ((1+x^(3*k+1))/(1-x^(3*k+1)))^2.
%F a(n) ~ exp(Pi*sqrt(2*n/3)) * Gamma(1/3)^2 / (2^(7/4) * 3^(5/12) * Pi^(4/3) * n^(7/12)).
%t nmax=60; CoefficientList[Series[Product[((1+x^(3*k+1))/(1-x^(3*k+1)))^2,{k,0,nmax}],{x,0,nmax}],x]
%Y Cf. A015128, A156616, A080054, A007096, A261610, A261651.
%K nonn
%O 0,2
%A _Vaclav Kotesovec_, Aug 28 2015