This tag is for questions involving square numbers. A non-negative integer $n$ is called a square number if $n = k^2$ for some integer $k$. Consider using with the [elementary-number-theory] or [number-theory] tags.

A number $n$ is a square number if and only if it is the square of an integer. That is, if $n = k^2$ for some integer $k$.

The name square number, or perfect square, comes from the fact that these particular numbers of objects can be arranged to fill a perfect square.

The square numbers begin $$0, 1, 4, 9, 16, 25, 36, 49, ...$$

The $k$th square number is given by $k^2$ with the zeroth square being $0$. Square numbers are strictly non-negative as $k^2 \ge 0$ for all real $k$. There are $\lfloor \sqrt{n} \rfloor+1$ square numbers in the range $[0, n]$.

References:

https://en.wikipedia.org/wiki/Square_number