A261610 - OEIS

%I #5 Aug 26 2015 12:19:31

%S 1,2,2,2,4,6,6,8,12,14,16,22,28,32,40,50,58,70,86,100,118,144,168,194,

%T 232,272,312,366,428,490,568,660,754,866,1000,1140,1300,1492,1696,

%U 1924,2196,2490,2812,3192,3610,4062,4588,5174,5806,6530,7342,8218,9208

%N Expansion of Product_{k>=0} (1 + x^(3*k+1))/(1 - x^(3*k+1)).

%F a(n) ~ exp(Pi*sqrt(n/3)) * Gamma(1/3) / (2^(5/3) * 3^(1/3) * Pi^(2/3) * n^(2/3)).

%t nmax = 60; CoefficientList[Series[Product[(1 + x^(3*k+1))/(1 - x^(3*k+1)), {k, 0, nmax}], {x, 0, nmax}], x]

%Y Cf. A015128, A080054, A261611.

%K nonn

%O 0,2

%A _Vaclav Kotesovec_, Aug 26 2015