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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 July 22 21:11 EDT 2024. Contains 374544 sequences. (Running on oeis4.)