The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A211061 Number of 2 X 2 matrices having all terms in {1,...,n} and determinant >= n. 3
 0, 3, 19, 69, 181, 411, 785, 1419, 2334, 3674, 5478, 7994, 11093, 15249, 20347, 26660, 34253, 43661, 54463, 67637, 82614, 100217, 120415, 143935, 169815, 199883, 233505, 271344, 313103, 360519, 411681, 469615, 532407, 601850, 677764 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 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 = 35; 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, n - 1], {n, 1, z1}] CROSSREFS Cf. A210000. Sequence in context: A091968 A158714 A064056 * A059599 A183461 A095662 Adjacent sequences:  A211058 A211059 A211060 * A211062 A211063 A211064 KEYWORD nonn AUTHOR Clark Kimberling, Mar 31 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 July 28 03:49 EDT 2021. Contains 346316 sequences. (Running on oeis4.)