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 A304080 #23 Oct 14 2019 04:28:18
%S A304080 1,1,-2,1,1,-2,-1,4,-1,-2,1,1,-2,-1,2,3,0,-6,0,3,2,-1,-2,1,1,-2,-1,2,
%T A304080 1,4,-4,-4,-2,0,10,0,-2,-4,-4,4,1,2,-1,-2,1,1,-2,-1,2,1,2,0,-2,-6,-2,
%U A304080 3,6,5,2,-3,-12,-3,2,5,6,3,-2,-6,-2,0,2,1,2,-1,-2,1
%N A304080 Triangular array T(n,k) giving coefficients in expansion of Product_{j=1..n} (1-x^j)^2.
%H A304080 Seiichi Manyama, <a href="/A304080/b304080.txt">Rows n = 0..30, flattened</a>
%e A304080 Irregular triangle starts:
%e A304080 n\k| 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
%e A304080 ---+-----------------------------------------------------------------------------
%e A304080 0 | 1;
%e A304080 1 | 1, -2, 1;
%e A304080 2 | 1, -2, -1, 4, -1, -2, 1;
%e A304080 3 | 1, -2, -1, 2, 3, 0, -6, 0, 3, 2, -1, -2, 1;
%e A304080 4 | 1, -2, -1, 2, 1, 4, -4, -4, -2, 0, 10, 0, -2, -4, -4, 4, 1, 2, -1, -2, 1;
%o A304080 (PARI) T(n, k) = polcoef(prod(j=1, n, (1-x^j)^2), k);
%o A304080 tabf(nn) = for(n=0, nn, for(k=0, n*(n+1), print1(T(n, k), ", ")); print)
%Y A304080 Cf. A002107, A231599, A303992.
%K A304080 sign,tabf
%O A304080 0,3
%A A304080 _Seiichi Manyama_, May 06 2018