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 A303402 #11 Apr 25 2018 02:56:41
%S A303402 1,-8,24,-72,344,-1416,5400,-21576,87000,-348296,1390872,-5560776,
%T A303402 22253784,-89025672,356055960,-1424186568,5696931032,-22787865096,
%U A303402 91150729368,-364602357960,1458412314456,-5833651510536,23334594559128,-93338369011272,373353522099288
%N A303402 Expansion of Product_{k>=1} (1 - 4*x^k)/(1 + 4*x^k).
%F A303402 a(n) ~ c * (-4)^n, where c = QPochhammer[-1, -1/4]/QPochhammer[-1/4] = 1.3264181585010678966173808329272239860188791629... - _Vaclav Kotesovec_, Apr 25 2018
%t A303402 nmax = 30; CoefficientList[Series[Product[(1 - 4*x^k)/(1 + 4*x^k), {k, 1, nmax}], {x, 0, nmax}], x] (* _Vaclav Kotesovec_, Apr 25 2018 *)
%o A303402 (PARI) N=66; x='x+O('x^N); Vec(prod(k=1, N, (1-4*x^k)/(1+4*x^k)))
%Y A303402 Expansion of Product_{k>=1} (1 - b*x^k)/(1 + b*x^k): A002448 (b=1), A303397 (b=2), A303398 (b=3), this sequence (b=4).
%Y A303402 Cf. A303387, A303391.
%K A303402 sign
%O A303402 0,2
%A A303402 _Seiichi Manyama_, Apr 23 2018