MathDB
Small number with big primes and big exponents

Source: Brazilian Undergrad MO 2019 Problem 5

May 17, 2022
Brazilian Undergrad MO 2019Brazilian Undergrad MOnumber theorycombinatoricscountinglimit

Problem Statement

Let M,k>0M, k>0 integers.
Let X(M,k)X(M,k) the (infinite) set of all integers that can be factored as p1e1p2e2prer{p_1}^{e_1} \cdot {p_2}^{e_2} \cdot \ldots \cdot {p_r}^{e_r} where each pip_i is not smaller than MM and also each eie_i is not smaller than kk.
Let Z(M,k,n)Z(M,k,n) the number of elements of X(M,k)X(M,k) not bigger than nn.
Show that there are positive reals c(M,k)c(M,k) and β(M,k)\beta(M,k) such that
limnZ(M,k,n)nβ(M,k)=c(M,k)\lim_{n \rightarrow \infty}{\frac{Z(M,k,n)}{n^{\beta(M,k)}}} = c(M,k)
and find β(M,k)\beta(M,k)