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%I #10 Jan 10 2017 22:07:14
%S 0,2,7,16,23,50,45,93,99,150,117,283,167,308,336,443,289,654,369,803,
%T 658,762,543,1392,779,1092,1086,1563,879,2160,1011,2038,1652,1888,
%U 1758,3323,1445,2386,2302,3730,1795,4220,1989,3889,3737
%N Number of 2 X 2 matrices having all terms in {1,...,n} and determinant n.
%C For a guide to related sequences, see A210000.
%H Chai Wah Wu, <a href="/A211053/b211053.txt">Table of n, a(n) for n = 1..3000</a>
%e a(2) counts these 2 matrices:
%e 2 1.....2 2
%e 2 2.....1 2
%t a = 1; b = n; z1 = 45;
%t t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]
%t c[n_, k_] := c[n, k] = Count[t[n], k]
%t Table[c[n, n], {n, 1, z1}] (* A211053 *)
%Y Cf. A210000.
%K nonn
%O 1,2
%A _Clark Kimberling_, Mar 31 2012
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