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 A209976 #10 Nov 22 2016 02:38:07
%S A209976 0,0,5,11,43,59,83,107,155,179,227,267,331,379,451,483,579,643,715,
%T A209976 787,915,963,1083,1171,1267,1347,1491,1563,1755,1867,1963,2083,2275,
%U A209976 2355,2547,2643,2835,2979,3195,3291,3483,3643,3787,3955,4275,4371
%N A209976 Number of 2 X 2 matrices having all elements in {0,1,...,n} and determinant 4.
%C A209976 See A210000 for a guide to related sequences.
%H A209976 Chai Wah Wu, <a href="/A209976/b209976.txt">Table of n, a(n) for n = 0..10000</a>
%t A209976 (See the Mathematica section at A210000.)
%Y A209976 Cf. A210000.
%K A209976 nonn
%O A209976 0,3
%A A209976 _Clark Kimberling_, Mar 16 2012