This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A211031 Number of 2 X 2 matrices having all elements in {0,1,...,n} and determinant in the closed interval [-n,n]. 4
 1, 16, 69, 176, 375, 650, 1107, 1626, 2413, 3326, 4527, 5782, 7689, 9436, 11753, 14354, 17491, 20458, 24623, 28334, 33425, 38438, 44031, 49450, 57323, 64028, 71849, 80078, 89857, 98468, 110545, 120388, 133117, 145382, 158699, 172256 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS For a guide to related sequences, see A210000. LINKS MATHEMATICA a = 0; 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] c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, -n, m}] Table[c1[n, n], {n, 0, z1}]  (* A211031 *) CROSSREFS Cf. A210000, A211032. Sequence in context: A299385 A299184 A299945 * A200839 A036660 A063493 Adjacent sequences:  A211028 A211029 A211030 * A211032 A211033 A211034 KEYWORD nonn AUTHOR Clark Kimberling, Mar 30 2012 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified October 21 06:01 EDT 2019. Contains 328291 sequences. (Running on oeis4.)