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 A209977 #10 Nov 22 2016 02:38:13
%S A209977 0,0,0,3,9,45,53,77,93,117,153,193,209,257,281,353,385,449,473,545,
%T A209977 617,665,705,793,825,985,1033,1105,1153,1265,1337,1457,1521,1601,1665,
%U A209977 1881,1929,2073,2145,2241,2385,2545,2593,2761,2841,3057,3145
%N A209977 Number of 2 X 2 matrices having all elements in {0,1,...,n} and determinant 5.
%C A209977 See A210000 for a guide to related sequences.
%H A209977 Chai Wah Wu, <a href="/A209977/b209977.txt">Table of n, a(n) for n = 0..10000</a>
%t A209977 (See the Mathematica section at A210000.)
%Y A209977 Cf. A210000.
%K A209977 nonn
%O A209977 0,4
%A A209977 _Clark Kimberling_, Mar 16 2012