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 A210289 #9 Dec 14 2016 08:35:03
%S A210289 1,5,9,15,25,29,35,53,63,81,85,89,107,141,159,165,193,197,215,261,271,
%T A210289 323,327,331,349,389,423,461,529,533,539,617,645,651,655,673,727,817,
%U A210289 863,959,969,973,1025,1131,1141,1159
%N A210289 Number of 2 X 2 matrices with all elements in {0,1,...,n} and permanent = (trace)^2.
%C A210289 See A210000 for a guide to related sequences.
%H A210289 Chai Wah Wu, <a href="/A210289/b210289.txt">Table of n, a(n) for n = 0..10000</a>
%t A210289 a = 0; b = n; z1 = 45;
%t A210289 t[n_] := t[n] = Flatten[Table[w^2 + z^2 + w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]
%t A210289 c[n_, k_] := c[n, k] = Count[t[n], k]
%t A210289 Table[c[n, 0], {n, 0, z1}] (* A210289 *)
%Y A210289 Cf. A210000.
%K A210289 nonn
%O A210289 0,2
%A A210289 _Clark Kimberling_, Mar 19 2012