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A210367 Number of 2 X 2 matrices with all elements in {0,1,...,n} and determinant >= 2n. 3
1, 0, 5, 26, 83, 203, 456, 853, 1497, 2477, 3860, 5690, 8305, 11470, 15684, 20947, 27328, 35057, 44569, 55569, 68849 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

See A210000 for a guide to related sequences.

LINKS

Chai Wah Wu, Table of n, a(n) for n = 0..1000

EXAMPLE

a(2)=5 counts these matrices:

2 0...2 1...2 0...2 0...2 2

0 2...0 2...1 2...2 2...0 2

MATHEMATICA

a = 0; b = n; z1 = 20;

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, 2 n - 1], {n, 0, z1}]

CROSSREFS

Cf. A210000.

Sequence in context: A145013 A096943 A166810 * A261347 A079909 A047669

Adjacent sequences:  A210364 A210365 A210366 * A210368 A210369 A210370

KEYWORD

nonn

AUTHOR

Clark Kimberling, Mar 20 2012

STATUS

approved

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Last modified April 25 19:05 EDT 2017. Contains 285426 sequences.