A037048 Number of pairs {i,j}, i>1, j>1, such that ij < n^2.

0, 3, 9, 20, 33, 54, 77, 108, 142, 186, 228, 285, 342, 409, 481, 563, 644, 742, 837, 946, 1060, 1184, 1308, 1449, 1592, 1744, 1903, 2076, 2240, 2432, 2618, 2818, 3028, 3246, 3461, 3702, 3940, 4192, 4444, 4719, 4980, 5274, 5559

Offset: 2

Author

Joe K. Crump (joecr(AT)carolina.rr.com)

Keywords

• nonn

Examples

			f(3)=3 because the only pairs of 2 numbers > 1 that are < 9 are (2,2) (2,3) (2,4).
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 2..1000

Crossrefs

Cf. A034806, A037092.

Programs

Mathematica

Table[Sum[Floor[(n^2-1)/i]+1-i,{i,2,n}],{n,2,45}] (* Harvey P. Dale, Oct 10 2011 *)

Formula

Sum(floor((n^2-1)/i)+1-i, i=2..n)