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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 …
GH from MO's user avatar
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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 …
GH from MO's user avatar
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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 …
GH from MO's user avatar
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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 …
GH from MO's user avatar
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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 …
GH from MO's user avatar
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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 …
GH from MO's user avatar
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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.
GH from MO's user avatar
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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 …
GH from MO's user avatar
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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 …
GH from MO's user avatar
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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 …
GH from MO's user avatar
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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 …
GH from MO's user avatar
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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 …
GH from MO's user avatar
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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{\ …
GH from MO's user avatar
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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 …
GH from MO's user avatar
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