Let φ k denote the kth iterate of Euler’s φ-function. We study two questions connected with these iterates. First, we determine the average order of φ k and 1/φ k ; e.g., we show that for each k ≥ 0, ån £ x jk+1(n) ~ frac3k! ekgp2fracx2(log3x)k (x®¥),sum_{n leq x} varphi_{k+1}(n) sim frac{3}{k! {rm e}^{kgamma}pi^2}frac{x^2}{(log_3{x})^k}qquad (xtoinfty),
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机译:令φ k sub>表示欧拉φ函数的第k次迭代。我们研究了与这些迭代有关的两个问题。首先,我们确定φ k sub>和1 /φ k sub>的平均阶数;例如,我们表明对于每个k≥0,å n£x sub> j k + 1 sub>(n)〜frac3k! e kg sup> p 2 sup> fracx 2 sup>(log 3 sub> x) k sup>(x® ¥),sum_ {n leq x} varphi_ {k + 1}(n)sim frac {3} {k! {rm e} ^ {kgamma} pi ^ 2} frac {x ^ 2} {(log_3 {x})^ k} qquad(xtoinfty),
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