New posts in Natural Numbers

Prove that when writing up all even numbers in a column, then chaining $2n+1$ from them, we get all natural numbers exactly once.

How to show $n=1+\sum_{k=1}^{n}\left\lfloor{\log_2\frac{2n-1}{2k-1}}\right\rfloor$ for every natural number $n$.

If a prime $p$ divides $n^2$ then it also divides $n$ - Is this proof correct?

Are there any two numbers such that multiplying them together is the same as putting their digits next to each other?

How many prime numbers in a given interval?

An endofunction on natural numbers defined by induction on $n$.

If the order in a set doesn’t matter, can we change order of, say, $\Bbb{N}$?

Finding the last two digits of the given number.

What IS the successor function without saying $S(n) = n + 1$?

Use an induction argument to prove that for any natural number $n$, the interval $(n,n+1)$ does not contain any natural number.