Average order of an arithmetic function: Difference between revisions

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Wgxli (talk | contribs)
Whoops, messed up the slope for sigma. Should be pi^2/12
Wgxli (talk | contribs)
The average order of r(n) is pi, while its cumulative sum grows as pi*n + O(sqrt(n)).
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* An average order of {{math|''σ''&#x200A;(''n'')}}, the [[Divisor function|sum of divisors]] of {{math|''n''}}, is {{math|''n''&#x200A;π<sup>2</sup>{{thinsp|/}}12}};
* An average order of {{math|''φ''&#x200A;(''n'')}}, [[Euler's totient function]] of {{math|''n''}}, is {{math|3&#x200A;''n''{{thinsp|/}}π<sup>2</sup>}};
* An average order of {{math|''r''&#x200A;(''n'')}}, the number of ways of expressing {{math|''n''}} as a sum of two squares, is {{math|π&#x200A;''n''}};
* The average order of representations of a natural number as a sum of three squares is {{math|4π&#x200A;''n''{{thinsp|/}}3}};
* The average number of decompositions of a natural number into a sum of one or more consecutive prime numbers is {{math|''n'' log&#x200A;2}};