"Email this user" was broken Aug 14 to 9am Aug 16. If you sent someone a message in this period, please send it again.
0,3
See A210000 for a guide to related sequences.
Chai Wah Wu, Table of n, a(n) for n = 0..1000
a(2)=5 counts these matrices:
2 0...2 1...2 0...2 0...2 2
0 2...0 2...1 2...2 2...0 2
a = 0; b = n; z1 = 20;
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, 2 n - 1], {n, 0, z1}]
Cf. A210000.
Sequence in context: A145013 A096943 A166810 * A261347 A079909 A047669
Adjacent sequences: A210364 A210365 A210366 * A210368 A210369 A210370
nonn
Clark Kimberling, Mar 20 2012
approved