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A211063 Number of 2 X 2 matrices having all terms in {1,...,n} and determinant >=3n.

%I A211063 #9 Jan 10 2017 23:02:44
%S A211063 0,0,0,0,8,38,122,284,589,1080,1848,2933,4515,6577,9366,12888,17444,
%T A211063 22928,29864,37986,48057,59656,73413,89307,108002,129068,153386,
%U A211063 180636,212111,246683,286126,329135,378047,431242,490425,555118
%N A211063 Number of 2 X 2 matrices having all terms in {1,...,n} and determinant >=3n.
%C A211063 For a guide to related sequences, see A210000.
%H A211063 Chai Wah Wu, <a href="/A211063/b211063.txt">Table of n, a(n) for n = 0..2000</a>
%t A211063 a = 1; b = n; z1 = 35;
%t A211063 t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]
%t A211063 c[n_, k_] := c[n, k] = Count[t[n], k]
%t A211063 s[n_, m_] := s[n, m] = Sum[c[n, k], {k, 1, m}]
%t A211063 Table[s[n,n^2]-s[n,3n-1],{n,1,z1}] (* A211063 *)
%Y A211063 Cf. A210000.
%K A211063 nonn
%O A211063 0,5
%A A211063 _Clark Kimberling_, Mar 31 2012
%E A211063 Offset corrected by _Chai Wah Wu_, Jan 10 2017