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A211153 Number of 2 X 2 matrices having all terms in {-n,...,0,..,n} and determinant >= 3n. 2
0, 20, 184, 804, 2284, 5408, 10780, 20084, 33664, 53840, 81124, 119156, 167872, 231096, 309816, 409128, 527088, 673112, 842776, 1049352, 1285760, 1561932, 1879908, 2247884, 2662000, 3134360, 3662256, 4264796, 4926892, 5673180 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For a guide to related sequences, see A210000.

LINKS

Table of n, a(n) for n=1..30.

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, 3n-1], {n, 1, z1}] (* A211153 *)

%/4 (* integers *)

CROSSREFS

Cf. A210000.

Sequence in context: A000144 A219581 A177073 * A210429 A047645 A010936

Adjacent sequences:  A211150 A211151 A211152 * A211154 A211155 A211156

KEYWORD

nonn

AUTHOR

Clark Kimberling, Apr 05 2012

STATUS

approved

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Last modified January 17 12:17 EST 2022. Contains 350394 sequences. (Running on oeis4.)