Let $\tau \left(n\right)$ be the number of divisors of $n$ ; let us define$$S_{\lambda }\left(x\right)=\left\{\begin{array}{cc}Card\left\{n\le x;\tau \left(n\right)\ge {(logx)}^{\lambda log2}\right\}\hfill & \mathrm{if}\lambda \ge 1\hfill \\ Card\left\{n\le x;\tau \left(n\right)\<{(logx)}^{\lambda log2}\right\}\hfill & \mathrm{if}\lambda \<1\hfill \end{array}\right.$$It has been shown that, if we set$$f(\lambda ,x)=\frac{x}{{(logx)}^{\lambda log\lambda -\lambda +1}\sqrt{loglogx}}$$the quotient $S\lambda \left(x\right)/f(\lambda ,x)$ is bounded for $\lambda$ fixed.$$ The aim of this paper is to give an explicit value for the inferior and superior limits of this quotient when $\lambda \ge 2$. For instance, when $\lambda =1/log2$, we prove$$liminf\frac{S_{\lambda }\left(x\right)}{f(\lambda ,x)}=0.938278681143\cdots$$and$$liminf\frac{S_{\lambda }\left(x\right)}{f(\lambda ,x)}=1.148126773469\cdots$$

Let Ω(n) and ω(n) denote the number of distinct prime factors of the positive integer n, counted respectively with and without multiplicity. Let $d_k\left(n\right)$ denote the Piltz function (which counts the number of ways of writing n as a product of k factors). We obtain a precise estimate of the sum ${\sum }_{n\le x,\Omega \left(n\right)-\omega \left(n\right)=q}f\left(n\right)$ for a class of multiplicative functions f, including in particular $f\left(n\right)=d_k\left(n\right)$, unconditionally if 1 ≤ k ≤ 3, and under some reasonable assumptions if k ≥ 4. The result also applies to f(n) = φ(n)/n (where φ is the totient...

E. Landau has given an asymptotic estimate for the number of integers up to x whose prime factors all belong to some arithmetic progressions. In this paper, by using the Selberg-Delange formula, we evaluate the number of elements of somewhat more complicated sets. For instance, if ω(m) (resp. Ω(m)) denotes the number of prime factors of m without multiplicity (resp. with multiplicity), we give an asymptotic estimate as x → ∞ of the number of integers m satisfying $2^{\omega \left(m\right)}m\le x$, all prime factors of m are congruent...

We consider the Legendre quadratic forms$${\varphi }_{ab}(x,y,z)=a{x}^2+b{y}^2-z^2$$and, in particular, a question posed by J–P. Serre, to count the number of pairs of integers $1\le a\le A,1\le b\le B$, for which the form ${\varphi }_{ab}$ has a non-trivial rational zero. Under certain mild conditions on the integers $a,b$, we are able to find the asymptotic formula for the number of such forms.

We consider an axiomatically-defined class of arithmetical semigroups that we call simple L-semigroups. This class includes all generalized Hilbert semigroups, in particular the semigroup of non-zero integers in any algebraic number field. We show, for all positive integers k, that the counting function of the set of elements with at most k distinct factorization lengths in such a semigroup has oscillations of logarithmic frequency and size $\surd x{\left(logx\right)}^{-M}$ for some M>0. More generally, we show a result on...