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A211060 Number of 2 X 2 matrices having all terms in {1,...,n} and determinant >n.

%I A211060 #11 Jan 07 2017 02:39:26
%S A211060 0,1,12,53,158,361,740,1326,2235,3524,5361,7711,10926,14941,20011,
%T A211060 26217,33964,43007,54094,66834,81956,99455,119872,142543,169036,
%U A211060 198791,232419,269781,312224,358359,410670,467577,530755,599962,676006
%N A211060 Number of 2 X 2 matrices having all terms in {1,...,n} and determinant >n.
%C A211060 For a guide to related sequences, see A210000.
%H A211060 Chai Wah Wu, <a href="/A211060/b211060.txt">Table of n, a(n) for n = 1..1000</a>
%t A211060 a = 1; b = n; z1 = 40;
%t A211060 t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]
%t A211060 c[n_, k_] := c[n, k] = Count[t[n], k]
%t A211060 c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, 0, m}]
%t A211060 Table[c1[n, n^2] - c1[n, n], {n, 1, z1}]
%Y A211060 Cf. A210000.
%K A211060 nonn
%O A211060 1,3
%A A211060 _Clark Kimberling_, Mar 31 2012