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A211062 Number of 2 X 2 matrices having all terms in {1,...,n} and determinant >= 2n. 2
0, 0, 5, 29, 93, 235, 493, 936, 1622, 2642, 4057, 6055, 8608, 12001, 16297, 21619, 28127, 36170, 45624, 57041, 70350, 85892, 103748, 124748, 148174, 175083, 205683, 239800, 277908, 321224, 368301, 421093, 479209, 543193, 613374 (list; graph; refs; listen; history; text; internal format)
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]

d[n_, m_] := d[n, m] = Sum[c[n, k], {k, 0, m}]

Table[d[n, n^2] - d[n, 2 n - 1], {n, 1, z1}]

CROSSREFS

Cf. A210000.

Sequence in context: A308396 A190585 A197276 * A264750 A205172 A139856

Adjacent sequences:  A211059 A211060 A211061 * A211063 A211064 A211065

KEYWORD

nonn

AUTHOR

Clark Kimberling, Mar 31 2012

STATUS

approved

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Last modified November 16 22:20 EST 2019. Contains 329208 sequences. (Running on oeis4.)