Top network posts

• 99 Prove that there are infinitely many primes with $666$ in their decimal representation without Dirichlet's theorem.
• 19 If $\lim_{n \rightarrow \infty} \frac{a_{n+1}}{a_n} = 0$, can $\sum_0^\infty a_n$ be rational?
• 13 Is the sum of all natural numbers countable?
• 13 Constructing a Möbius strip using a square paper? Is it possible?
• 11 There cannot be an infinite AP of perfect squares.
• 10 Any finite group can be realized as a subgroup of the group of symmetries of a regular polytope?
• 9 Is the sum of reciprocals of all products from $2$ to $n-1$ always $0.5n-1$?
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