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Asymptotic behavior of functions, asymptotic series and related topics

12 votes
Accepted

Asymptotics of a recurrence relation

It is not hard prove the bounds you want by purely real variable techniques. First note that the $a_n$ are non-negative for all $n$. For a general non-negative sequence $a_n$, and real numbers $N>0$, …
Lucia's user avatar
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3 votes
Accepted

Mean time to get $k$ heads for a coin with growing bias

If one argues carefully using the saddle point method, one could obtain asymptotics for $P(k,y)$; as the argument above indicates, the likely values of $y$ are sharply concentrated around $\sqrt{2nk} … For larger $k$ one can use the previous argument of bounding the probability away from the peak (or work harder and get asymptotics using the saddle point method). …
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13 votes
Accepted

Asymptotic behavior of $\{\text{#}(a,x,b,y)\in \mathbb{N^4}| \text{ }ax+by=n\}$ for large $n$

This is a binary additive divisor problem (also known as the shifted convolution problem) and related questions are to understand asymptotics for $\sum_{n\le x} d(n) d(n+k)$, or $\sum_{n\le x} \lambda_f …
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7 votes
Accepted

Estimating size of greatest prime divisor of a sequence of integers

The sequence grows too rapidly and I doubt that one can get meaningful asymptotics for the largest prime factor. …
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4 votes
Accepted

Asymptotics of the number of elements in the intersection of two growing sets

But we can continue with actual inequalities rather than asymptotics. Consider the probability that the size of the intersection is at most $J$ (and assume that $J\le p^2/(n-2p)$). …
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2 votes

Asymptotic value of a multivariate integral

It may be possible to refine this to get asymptotics but I have not thought about that. …
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14 votes
Accepted

Asymptotic behavior of the sequence $u_n = u_{n-1}^2-n$

For general $\alpha >1$, a similar argument would show very good asymptotics for large $n$. …
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12 votes
Accepted

Prove or disprove that $\sup_{n\in\mathbb{N}}\left|\sum_{\substack{d|n \\d<Q}}\mu(d)\right|\...

This is not true. In fact $$ x(\log x)^{-1+1/\pi} \gg \sup_n \Big| \sum_{\substack{ d|n \\ d\le x}} \mu(d) \Big| \gg x (\log x)^{-1+1/\pi}. $$ The upper bound is due to Montgomery and Vaughan (see …
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7 votes
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Estimating the number of functions which are at most $c$-to-$1$ for some constant $c \ge 2$

point method, and typically one would get that the contribution to the integral around $z= r$ is dominant, and that there is an arc (probably of length about $1/\sqrt{n}$ around $r$) which will give fine asymptotics
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12 votes
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Mean of i.i.d Random Variables With No Expected Value

We can attack this problem by using Fourier transforms (i.e. characteristic functions). I'll consider the example in the problem where $X$ is a random variable taking the value $0$ with probabilit …
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16 votes
Accepted

Asymptotic density of k-almost primes

I'll address Joel's edited question of getting good asymptotics on RH. … The usual way in which such results are carried out in the literature is to start with asymptotics for coefficients of $\zeta(s)^z$ for complex $z$, and then to use the saddle point method to identify …
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10 votes
Accepted

Bound on sum of complex summands involving binomial coefficients

Assuming that $|x+y|<1$ and $4|xy| \le 1$, here's a proof of the decay. First suppose that $|x|> |y|$. The desired sum is $$ \le \binom{2n}{n} |xy|^n \sum_{j=0}^{n} |y/x|^j \le \binom{2n}{n} |x …
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22 votes
Accepted

Are the asymptotics of A003238 known?

One can obtain more precise asymptotics by working harder with the argument below. …
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