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

0, 1, 12, 53, 158, 361, 740, 1326, 2235, 3524, 5361, 7711, 10926, 14941, 20011, 26217, 33964, 43007, 54094, 66834, 81956, 99455, 119872, 142543, 169036, 198791, 232419, 269781, 312224, 358359, 410670, 467577, 530755, 599962, 676006

Offset

1,3

Comments

For a guide to related sequences, see A210000.

Links

Chai Wah Wu, Table of n, a(n) for n = 1..1000

Mathematica

a = 1; b = n; z1 = 40;
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, 0, m}]
Table[c1[n, n^2] - c1[n, n], {n, 1, z1}]

Crossrefs

Cf. A210000.

Sequence in context: A268186 A253130 A213549 * A242514 A030182 A060171

Adjacent sequences: A211057 A211058 A211059 * A211061 A211062 A211063

Keyword

nonn

Author

Clark Kimberling, Mar 31 2012

Status

approved