A211142 Number of 2 X 2 matrices having all terms in {-n,...,0,...,n} and determinant n+1.

0, 4, 24, 116, 128, 408, 296, 788, 748, 1232, 888, 2488, 1312, 2568, 2664, 3860, 2352, 5652, 3032, 6864, 5320, 6456, 4520, 12152, 6356, 9264, 9000, 13288, 7392, 18440, 8520, 17556, 13576, 16032, 14216, 28612

Offset

0,2

Comments

For a guide to related sequences, see A210000.

Links

Chai Wah Wu, Table of n, a(n) for n = 0..3000

Mathematica

a = -n; b = n; z1 = 35;
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 + 1], {n, 0, z1}]   (* A211142 *)
%/4                              (* integers *)

Crossrefs

Cf. A210000.

Sequence in context: A300581 A099582 A295093 * A374389 A272735 A295547

Adjacent sequences: A211139 A211140 A211141 * A211143 A211144 A211145

Keyword

nonn

Author

Clark Kimberling, Apr 03 2012

Status

approved