This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A375108 #13 Jul 30 2024 14:41:18
%S A375108 1,-1,0,2,0,-2,2,0,0,0,0,0,2,-1,0,2,-1,-2,2,0,0,0,0,2,2,-2,0,0,0,-2,2,
%T A375108 0,0,2,0,0,2,-2,-2,2,1,-2,2,2,0,-1,0,0,2,-4,0,2,0,0,2,0,0,2,0,0,0,-2,
%U A375108 0,2,0,-2,2,0,0,0,0,-2,2,0,2,2,0,-2,2,0,0,-1,-2,2,2,-2,0,2,-1,-2,2,2,0,0,0
%N A375108 Expansion of Sum_{k in Z} x^(3*k) / (1 - x^(7*k+3)).
%H A375108 R. P. Agarwal, <a href="https://www.ias.ac.in/describe/article/pmsc/103/03/0269-0293">Lambert series and Ramanujan</a>, Prod. Indian Acad. Sci. (Math. Sci.), v. 103, n. 3, 1993, pp. 269-293. see p. 286.
%F A375108 G.f.: Product_{k>0} (1-x^(7*k))^2 * (1-x^(7*k-1)) * (1-x^(7*k-6)) / ((1-x^(7*k-3)) * (1-x^(7*k-4)))^2.
%o A375108 (PARI) my(N=100, x='x+O('x^N)); Vec(sum(k=-N, N, x^(3*k)/(1-x^(7*k+3))))
%o A375108 (PARI) my(N=100, x='x+O('x^N)); Vec(prod(k=1, N, (1-x^(7*k))^2*(1-x^(7*k-1))*(1-x^(7*k-6))/((1-x^(7*k-3))*(1-x^(7*k-4)))^2))
%Y A375108 Cf. A375106, A375107.
%K A375108 sign
%O A375108 0,4
%A A375108 _Seiichi Manyama_, Jul 30 2024