90 What is the smallest integer greater than 1 such that $\frac12$ of it is a perfect square and $\frac15$ of it is a perfect fifth power? 87 What proportion of positive integers have two factors that differ by 1? 81 Help with a prime number spiral which turns 90 degrees at each prime 61 Is it possible to have 2 different but equal size real number sets that have the same mean and standard deviation? 56 Infinite area under curve without using derivatives and integrals

### Reputation (56,625)

 +10 What is the chance we flip the coin $10$ or more times? +25 Continued fractions with a bounded sequence of terms +10 What is the smallest integer greater than 1 such that $\frac12$ of it is a perfect square and $\frac15$ of it is a perfect fifth power? +10 How to solve $y^3=x(x+1)$ where $x$ and $y$ are integers?

### Questions (46)

 19 Very elementary proof of that Euler's totient function is multiplicative 14 Are dense subsets almost nothing or almost everything? 10 A topology over $\Bbb N$ based on convergence of series. 9 $0<|\sqrt a-\sqrtb|<\epsilon$ for $a,b\in\Bbb Z_+$ 9 Let $A\subset\Bbb N$ such that for all $a\in A,b\in\Bbb N$, there exists some $c$ such that $a+bc$ is a square. What is $A\cap\{1,2,\dots,2018\}$?

### Tags (399)

 561 calculus × 244 283 abstract-algebra × 143 451 real-analysis × 228 280 limits × 108 430 number-theory × 173 267 sequences-and-series × 132 423 elementary-number-theory × 207 238 prime-numbers × 61 397 algebra-precalculus × 133 213 linear-algebra × 121