A211053 Number of 2 X 2 matrices having all terms in {1,...,n} and determinant n.

0, 2, 7, 16, 23, 50, 45, 93, 99, 150, 117, 283, 167, 308, 336, 443, 289, 654, 369, 803, 658, 762, 543, 1392, 779, 1092, 1086, 1563, 879, 2160, 1011, 2038, 1652, 1888, 1758, 3323, 1445, 2386, 2302, 3730, 1795, 4220, 1989, 3889, 3737

Offset

1,2

Comments

For a guide to related sequences, see A210000.

Links

Chai Wah Wu, Table of n, a(n) for n = 1..3000

Example

a(2) counts these 2 matrices:
2 1.....2 2
2 2.....1 2

Mathematica

a = 1; b = n; z1 = 45;
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]
Table[c[n, n], {n, 1, z1}]  (* A211053 *)

Crossrefs

Cf. A210000.

Sequence in context: A225323 A167236 A041573 * A041341 A296857 A229595

Adjacent sequences: A211050 A211051 A211052 * A211054 A211055 A211056

Keyword

nonn

Author

Clark Kimberling, Mar 31 2012

Status

approved