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 A209973 #15 Nov 29 2016 08:00:24
%S A209973 0,0,12,20,36,52,76,100,132,156,204,244,276,324,396,428,492,556,628,
%T A209973 700,764,812,932,1020,1084,1164,1308,1380,1476,1588,1684,1804,1932,
%U A209973 2012,2204,2300,2396,2540,2756,2852,2980,3140,3284,3452,3612,3708
%N A209973 Number of 2 X 2 matrices having all elements in {0,1,...,n} and determinant 2.
%C A209973 See A210000 for a guide to related sequences.
%H A209973 Chai Wah Wu, <a href="/A209973/b209973.txt">Table of n, a(n) for n = 0..10000</a>
%F A209973 a(n) = A197168(n) + 4*n + 2 for n >= 2. - _Chai Wah Wu_, Nov 28 2016
%t A209973 (See the Mathematica section at A210000.)
%Y A209973 Cf. A210000.
%K A209973 nonn
%O A209973 0,3
%A A209973 _Clark Kimberling_, Mar 16 2012