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 A209457 #25 Jan 04 2018 02:51:13
%S A209457 1,1,-1,-1,0,0,-1,-1,1,2,0,-2,0,2,0,-3,0,4,1,-4,-2,4,2,-5,-3,6,5,-5,
%T A209457 -6,5,6,-7,-8,7,11,-5,-12,5,13,-6,-16,5,19,-3,-21,2,23,-2,-26,0,30,4,
%U A209457 -32,-6,34,7,-39,-12,43,18
%N A209457 Expansion of x^7*Product_{i>=0} ((1 + x^(2*i - 1))*(1 - x^(4*i - 5))).
%C A209457 Expansion of x^7 QPochhammer[1/x^5, x^4] QPochhammer[-(1/x), x^2].
%D A209457 George E. Andrews, Number Theory, Dover Publications, N.Y., 1971, 164-165.
%D A209457 Samuel I. Goldberg, Curvature and Homology, Dover, New York, 1998, 144.
%H A209457 G. C. Greubel, <a href="/A209457/b209457.txt">Table of n, a(n) for n = 0..1000</a>
%e A209457 Series[x^7 QPochhammer[1/x^5, x^4] QPochhammer[-(1/x), x^2], {x, 0, 10}] = 1+x-x^2-x^3-x^6-x^7+x^8+2*x^9+O[x]^11.
%t A209457 Table[SeriesCoefficient[Series[x^7*Product[(1 + x^(2*i - 1))*(1 - x^(4*i - 5)), {i, 0, Infinity}], {x, 0, 100}], n], {n, 0, 100}]
%Y A209457 Cf. A207944.
%K A209457 sign
%O A209457 0,10
%A A209457 _Roger L. Bagula_, Mar 09 2012