A307757 - OEIS

%I #45 May 07 2021 05:09:48

%S 1,-1,0,0,-1,0,2,-2,0,2,-2,0,4,-4,0,4,-5,0,8,-8,0,8,-10,0,14,-15,0,16,

%T -18,0,24,-26,0,28,-32,0,42,-44,0,48,-54,0,68,-72,0,80,-88,0,108,-115,

%U 0,128,-140,0,170,-180,0,200,-218,0,260,-276,0,308,-333,0,392,-416,0,464

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

%t m = 70; CoefficientList[Series[Product[1/(1 + x^k/(1 + x^(2*k))), {k, 1, m}], {x, 0, m}], x] (* _Amiram Eldar_, May 07 2021 *)

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

%Y Cf. A309733, A327686, A327688.

%K sign

%O 0,7

%A _Seiichi Manyama_, Sep 22 2019