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 A210002 #7 Nov 27 2016 21:20:11
%S A210002 0,0,0,4,16,26,44,62,104,122,164,198,256,298,364,390,480,538,604,670,
%T A210002 792,834,948,1030,1120,1194,1332,1398,1584,1690,1780,1894,2080,2154,
%U A210002 2340,2430,2616,2754,2964,3054,3240,3394,3532,3694,4008,4098
%N A210002 Number of 2 X 2 matrices having all elements in {1,2,...,n} and determinant 4.
%C A210002 See A210000 for a guide to related sequences.
%H A210002 Chai Wah Wu, <a href="/A210002/b210002.txt">Table of n, a(n) for n = 0..10000</a>
%t A210002 (See the Mathematica section at A209978.)
%Y A210002 Cf. A210000.
%K A210002 nonn
%O A210002 0,4
%A A210002 _Clark Kimberling_, Mar 16 2012