A211151 Number of 2 X 2 matrices having all terms in {-n,...,0,...,n} and determinant > n.

24, 196, 784, 2304, 5324, 10964, 19756, 33772, 53496, 81396, 118452, 168324, 229964, 310132, 407964, 527644, 670888, 844896, 1045916, 1286220, 1560508, 1879548, 2244404, 2664180, 3130076, 3663856, 4260240, 4927920, 5665992

Offset

1,1

Comments

For a guide to related sequences, see A210000.

Links

Table of n, a(n) for n=1..29.

Mathematica

a = -n; b = n; z1 = 30;
t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]
c[n_, k_] := c[n, k] = Count[t[n], k]
c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, -2*n^2, m}]
Table[c1[n, 2*n^2]-c1[n, n-1], {n, 1, z1}] (*A211151*)
%/4  (* integers *)

Crossrefs

Cf. A210000.

Sequence in context: A220296 A282286 A123197 * A125361 A126519 A260358

Adjacent sequences: A211148 A211149 A211150 * A211152 A211153 A211154

Keyword

nonn

Author

Clark Kimberling, Apr 04 2012

Status

approved