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Asymptotic behavior of functions, asymptotic series and related topics
42
votes
Accepted
Wrong asymptotics of OEIS A000607 (number of partitions of an integer in prime parts)?
Your data is compatible with the more refined estimates proved by Vaughan in Ramanujan J. 15 (2008), 109–121. His Theorems 1 and 2 (together with his (1.9)) reveal that
$$\log(A000607(n)) = 2 \pi \sq …
14
votes
Accepted
Probability that a positive integer is in the range of the Euler phi function
See Erick Wong's response here. In particular, Kevin Ford proved (in more precise form) that
$$ f(n) = \frac{n}{\log n} \exp\left(O(\log \log \log n)^2\right),$$
whence $f(n)/n$ tends to zero. The sam …
12
votes
Accepted
The number of representations of an integer as the inner product of integral lattice points
The asymptotic formula is true for even dimensions $k\geq 2$. We can prove this by induction on $k$, inspired by Rodrigo's observation on Eisenstein series.
The case $k=2$ is classical and addressed …
12
votes
Accepted
About the logarithmic derivative of the Riemann zeta function
I think your final goal follows by taking the logarithmic derivative of the functional equation:
$$\frac{\zeta'}{\zeta}(s)+\frac{\zeta'}{\zeta}(1-s)=\log\pi-\frac{1}{2}\frac{\Gamma'}{\Gamma}\left(\fra …
12
votes
What is the asymptotic of the irregular blue curve? Is it $(8x)^{1/2}$ or is it something else?
Let us denote the left hand side of $(1)$ by $\psi(x)$. It is known that $|\psi(x)-x|$ is not bounded by a constant times $x^{1/2}$. In fact Littlewood (1914) proved that
$$\psi(x)-x=\Omega_{\pm}(x^{1 …
12
votes
Accepted
Lindelöf hypotheses for derivatives of zeta
The Lindelöf hypothesis yields the same bound for each derivative of $\zeta(s)$ via Cauchy's formula. Indeed, let $n\in\mathbb{N}$, $\sigma\in\mathbb{R}$, $T\in(1,\infty)$, $\varepsilon\in(0,1/2)$. Le …
10
votes
Accepted
$n$th prime: a better approximation
You can find an in-depth answer to your question in this paper of de Reyna and Jeremy. See in particular (65)-(66) along with (30) and Theorem 4.9. See also Theorem 6.2.
10
votes
Accepted
Does the Riemann hypothesis predict a bound for this prime-counting function?
The Riemann hypothesis is equivalent to the following statement:
$$f(x)=\mathrm{li(x)}-\frac{x}{\log x}+O(\sqrt{x}),\qquad x\geq 2.$$
Note that
$$\mathrm{li(x)}=\mathrm{li(2)}+\frac{x}{\log x}-\frac{2 …
9
votes
Accepted
Asymptotics of "ugly" function elucidate Goldbach's conjecture?
Your sum can be rewritten as
$$ D(N)=\sum_{n=1}^{N-1}d(n)d(N-n),$$
where $N=2c$, and $d(m)$ is the number of divisors of $m$. This is a so-called "binary additive divisor sum", and it has been studied …
9
votes
Accepted
Asymptotics for sums of powers of divisor function
Yes, these are standard things in analytic number theory. We have
$$ \sum_{n=1}^\infty\frac{\tau(n)^k}{n^s}=\zeta(s)^{2^k}F_k(s),\qquad\Re(s)>1,$$
where $F_k(s)$ is an explicit Dirichlet series that c …
9
votes
Estimate related to the Möbius function
You can derive a very precise asymptotic expansion of your quantity by the Selberg-Delange method.
I recommend that you adapt, to your situation, the arguments of Section II.6.1 of Tenenbaum: Introd …
9
votes
Accepted
Determining the asymptotic behavior of a series
This is my third response. I claim that for $0 < t < 1$ we have the uniform bounds
$$ \liminf_{n\to\infty}\ nt f_n(t) = \frac{-1}{\log\mu}+O(1),$$
$$ \limsup_{n\to\infty}\ nt f_n(t) = \frac{-1}{\log\m …
9
votes
Accepted
Asymptotic estimate for an integral involving the squared modulus of the Riemann zeta function
Let us introduce the notation
$$M(T):=\int_0^T|\zeta(\sigma+it)|^2\,dt.$$
Then
$$\int_0^T \frac{|\zeta(\sigma+it)|^2}{\sqrt{1+t^2}} \,dt=\int_0^T\frac{dM(t)}{\sqrt{1+t^2}}=\frac{M(T)}{\sqrt{1+T^2}}+\i …
9
votes
Accepted
Sum over reciprocal of primes times coefficient
The sum in question equals
\begin{align*}\sum_{p\leq x}\frac{1}{p^{1+2/\log x}}\left(\frac{\log\left(x/p\right)}{\log(x)}\right)^2
&=\sum_{p\leq x}\frac{1}{p}e^{-2\frac{\log p}{\log x}}\left(1-\frac{\ …
8
votes
Is there a "convolution" of asymptotic growth?
$F(H)$ and $G(H)$ do not determine the asymptotic growth of the third display. Indeed, consider the following two functions from $\mathbb{Z}_{\geq 0}$ to $\mathbb{Z}_{\geq 0}$:
$$
f(x):=\begin{cases}0 …