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A037048
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Number of pairs {i,j}, i>1, j>1, such that ij < n^2.
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3
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,2
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LINKS
| Harvey P. Dale, Table of n, a(n) for n = 2..1000
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FORMULA
| Sum(floor((n^2-1)/i)+1-i, i=2..n)
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EXAMPLE
| f(3)=3 because the only pairs of 2 numbers > 1 that are < 9 are (2,2) (2,3) (2,4).
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MATHEMATICA
| Table[Sum[Floor[(n^2-1)/i]+1-i, {i, 2, n}], {n, 2, 45}] (* From Harvey P. Dale, Oct 10 2011 *)
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CROSSREFS
| Cf. A034806, A037092.
Sequence in context: A073716 A174866 A187409 * A139142 A037257 A145068
Adjacent sequences: A037045 A037046 A037047 * A037049 A037050 A037051
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KEYWORD
| nonn
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AUTHOR
| Joe K. Crump (joecr(AT)carolina.rr.com)
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