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A211053 Number of 2 X 2 matrices having all terms in {1,...,n} and determinant n.

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