Tag: elementary-number-theory
- The divisibility problem
- Can a number written only with zeros, threes, fives, sevens and eights be a perfect square
- Is there a finite set of distinct naturals whose reciprocals sum to 1, and no element in the set is one less than a prime
- A quick, more elementary way to show $(\mathbb{Z}/16 \mathbb{Z})^{\times} \cong C_4 \times C_2$
- If n = aaaaaaaaabcd how many of them are divisible by 45 such that $a \neq 0$ and a,b,c,d are not necessarily distinct.
- Sequences of the form $A(n) = A(A(n-1)\bmod n)^2$
- Perfect cubes with digit-average at least $7.5$
- Expressing $\frac{2}{n}$ as the sum of two unit fractions
- Is there a dense subset of the rationals (between 0 and 1) that doesn’t include its midpoints
- Combinatorics style number theory