cp's OEIS Frontend

A211056 Number of 2 X 2 nonsingular matrices having all terms in {1,...,n}.

%I A211056 #6 Jan 14 2017 01:36:57
%S A211056 0,10,66,224,576,1210,2290,3936,6352,9722,14322,20304,28080,37834,
%T A211056 49922,64704,82624,103898,129170,158640,192944,232554,278050,329680,
%U A211056 388368,454522,528770,611680,704192,806490,919890,1044624,1181680
%N A211056 Number of 2 X 2 nonsingular matrices having all terms in {1,...,n}.
%C A211056 A211056(n) + A134506(n) = n^4.
%C A211056 For a guide to related sequences, see A210000.
%t A211056 a = 1; b = n; z1 = 35;
%t A211056 t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]
%t A211056 c[n_, k_] := c[n, k] = Count[t[n], k]
%t A211056 c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, 0, m}]
%t A211056 Table[c1[n, n^2] - c[n, 0], {n, 1, z1}]   (* A211059 *)
%t A211056 2*%     (* A211056 *)
%Y A211056 Cf. A134506, A210000, A211059.
%K A211056 nonn
%O A211056 1,2
%A A211056 _Clark Kimberling_, Mar 31 2012