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 A211070 #6 Jan 14 2017 01:37:38
%S A211070 1,10,43,118,263,474,831,1258,1893,2652,3685,4748,6375,7918,9931,
%T A211070 12216,15015,17654,21395,24726,29253,33822,39011,43906,50995,57210,
%U A211070 64431,71968,81075,88962,100159,109346,121107,132636,145097
%N A211070 Number of 2 X 2 matrices having all terms in {1,...,n} and determinant d satisfying -n < d < n.
%C A211070 For a guide to related sequences, see A210000.
%t A211070 a = 1; b = n; z1 = 35;
%t A211070 t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]
%t A211070 c[n_, k_] := c[n, k] = Count[t[n], k]
%t A211070 c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, -n, m}]
%t A211070 Table[c1[n, n - 1] - c1[n, -n], {n, 1, z1}] (* A211070 *)
%Y A211070 Cf. A210000.
%K A211070 nonn
%O A211070 1,2
%A A211070 _Clark Kimberling_, Mar 31 2012