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for questions about sequences and series, e.g. convergence, closed form expressions, etc. Note that there is a different tag for spectral sequences, and also note that MathOverflow is not for homework. Please consider consulting the online encyclopedia for integer sequences, if you are trying to identify a given sequence that you have found in your research.

6 votes
0 answers
149 views

Tweak the numerators in the alternating harmonic series so that the partial sums alternate a...

I was thinking about the alternating harmonic series: $1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+\cdots$. I wondered what would happen if we tweak the numerators so that the partial sums alternate between …
Dan's user avatar
  • 3,507
25 votes
3 answers
2k views

Does there exist a continuous function $f(x)$ such that $f(0)=0$ and $0<\lim_{n\to\infty}\pr...

Does there exist a continuous function $f(x)$ such that $f(0)=0$ and $0<\lim\limits_{n\to\infty}\prod\limits_{k=1}^n f(\frac{k}{n})<\infty$ ? I do not see any reason why such a function could not exis …
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  • 3,507
31 votes
5 answers
2k views

On average, how many uniformly random real numbers $u$ are needed for their sum to exceed $1...

A well-known question is: on average, how many uniformly random real numbers in $(0,1)$ are needed for their sum to exceed $1$? The answer is $e$. Let's tweak this question by making each random numbe …
Dan's user avatar
  • 3,507
0 votes

You have $n$ rectangles of area $1$ and variable height. Pack as many as possible in a semic...

I have evidence that, for large $n$, the number of leftover rectangles is approximately $\color{red}{\frac16\log{n}+c}$, where $c\approx 0.482$. We will pack the circles from $\color{red}{\text{top to …
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15 votes
0 answers
387 views

Will a unit disk be completely covered by randomly placed disks of area $\pi,\frac{\pi}{2},\...

On a "bottom" disk of area $\pi$, we place "top" disks of area $\pi,\frac{\pi}{2},\frac{\pi}{3},\dots$ such that the centre of each top disk is an independent uniformly random point on the bottom disk …
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  • 3,507
0 votes
1 answer
107 views

If $a_1=1$ and $a_n=\sec (a_{n-1})$ then what does the proportion of positive terms approach...

Consider the sequence $a_1=1$ and $a_n=\sec (a_{n-1})$ for $n>1$. What does the proportion of positive terms approach, as $n\to\infty$? At first I thought the limiting proportion might be $\frac{1} …
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  • 3,507
9 votes
1 answer
430 views

You have $n$ rectangles of area $1$ and variable height. Pack as many as possible in a semic...

You have $n$ rectangles of area $1$ and variable height. Pack as many of these rectangles as possible in a semicircle of area $n$. How many leftover rectangles will there be, in terms of $n$? How to p …
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  • 3,507