A327720 - OEIS

%I #17 Sep 23 2019 09:22:48

%S 1,1,1,1,2,3,3,3,4,6,7,9,10,12,14,17,21,23,26,32,40,46,51,57,68,80,91,

%T 102,115,135,156,180,197,219,250,290,333,364,403,456,526,594,648,708,

%U 803,922,1037,1128,1223,1373,1560,1752,1902,2062,2300,2613,2926,3149,3378,3740

%N Expansion of Product_{k>=1} (1 + x^k/(1 + x^(2*k)/(1 + x^(3*k)/(1 + x^(4*k)/(1 + x^(5*k)))))).

%C a(169) = -3504817 < 0.

%H Seiichi Manyama, <a href="/A327720/b327720.txt">Table of n, a(n) for n = 0..1000</a>

%t nmax = 60; CoefficientList[Series[Product[(1 + x^k/(1 + x^(2*k)/(1 + x^(3*k)/(1 + x^(4*k)/(1 + x^(5*k)))))), {k, 1, nmax}], {x, 0, nmax}], x] (* _Vaclav Kotesovec_, Sep 23 2019 *)

%o (PARI) N=66; x='x+O('x^N); Vec(prod(k=1, N, 1+x^k/(1+x^(2*k)/(1+x^(3*k)/(1+x^(4*k)/(1+x^(5*k)))))))

%Y Cf. A327716, A327717, A327718, A327719.

%K sign,look

%O 0,5

%A _Seiichi Manyama_, Sep 23 2019