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A210285 Number of 2 X 2 matrices with all elements in {0,1,...,n} and determinant floor(n/2). 2
1, 10, 7, 15, 36, 52, 65, 89, 155, 179, 153, 193, 374, 422, 287, 319, 617, 681, 584, 656, 914, 962, 639, 727, 1705, 1785, 889, 961, 1672, 1784, 1768, 1888, 2496, 2576, 1483, 1579, 3460, 3604, 1843, 1939, 4177, 4337, 3298, 3466, 3886, 3982 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

See A210000 for a guide to related sequences.

LINKS

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

MATHEMATICA

a = 0; 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, Floor[n/2]], {n, 0, z1}]   (* A210285 *)

CROSSREFS

Cf. A210000.

Sequence in context: A016731 A324087 A068444 * A190996 A210283 A227473

Adjacent sequences:  A210282 A210283 A210284 * A210286 A210287 A210288

KEYWORD

nonn

AUTHOR

Clark Kimberling, Mar 19 2012

STATUS

approved

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Last modified September 19 06:16 EDT 2020. Contains 337177 sequences. (Running on oeis4.)