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45
Multiple-choice: sum of primes below $1000$
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35
Prove that 10101...10101 is NOT a prime.
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33
What is a square root?
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25
How to prove that $\frac{1000!}{(500!)^2}$ is not divisible by 7?
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20
Prove $\frac{a^3+b^3+c^3}{3}\frac{a^7+b^7+c^7}{7} = \left(\frac{a^5+b^5+c^5}{5}\right)^2$ if $a+b+c=0$
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18
Sum of all Fibonacci numbers $1+1+2+3+5+8+\cdots = -1$?
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17
Finding how many 8-bit bytes contain an even number of zeros . . .
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15
Evaluate the limit at infinity
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13
Simple method to solve a geometry question for junior high school student
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12
Handshakes in a party
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11
Show that $45<x_{1000}<45.1$
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11
Why does "$x^2 - 5x + 6 = 0$", which is the same as "$(x-3)(x-2) = 0$", represent a parabola?
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11
Number of ways of visiting N places
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10
Find $x$ positive integer such that $x^4+x^3+x^2+x+1$ is a perfect square
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10
Proof of an inequality using Cauchy's inequality: $\sum_{k=1}^n \left(p_k+\frac{1}{p_k}\right)^2\geq n^3+2n+\frac{1}{n}$
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10
Composition of Piecewise Function Limit
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10
$P(x)=\frac{x}{x+1}$ for $x=1,2,...,n$, find the value of $P(n+1)$.
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10
Prove that $a<b+\epsilon$ for all $\epsilon>0$ implies $a\le b$
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10
Prove the inequality $\frac{a+c}{a+b}+\frac{b+d}{b+c}+\frac{c+a}{c+d}+\frac{d+b}{d+a}\geq 4$
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10
Show that if $f'$ is strictly increasing, then $\frac{f(x)}{x}$ is increasing over $(0,\infty)$
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9
Could be this : $7131372917538397234773191167617941438959$ written as $x^{2}+y^{2}$ with $x, y$ integers?
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9
Can both $n+3\; \text{and}\; n^2+3$ both be cubic numbers at same time?
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9
How do I solve $e^{\sin(x)} - e^{-\sin(x)}= 4?$
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9
How to solve this limit without L'Hospital?
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9
Prove that it is impossible to have integers $b=5a$ under a digit re-ordering
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9
Solution of functional equation $f(x+y)=f(x)+f(y)+y\sqrt{f(x)}$
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9
What is $\gcd(n-1,n+10)$, for $n$ a natural number?
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8
How is "point" in geometry undefined? And What is a "mathematical definition"?
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8
Does sum of the reciprocals of all the composite numbers converge?
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8
Find the maximum of positive integer $k$ so that for all positive real numbers $x$ we have: $x^6+x^5+x^4+x^2+x+4>kx^3$
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