I was playing the game $24$, and I saw that some numbers, such as $5,8,9,10$, could not be multiplied, divided, subtracted, added, etc. by me to get $24$ no matter how hard I tried...
Question: So that got me thinking: Is there a way to tell if a set of $4$ numbers can be manipulated to make $24$?
You can use any operation sign and any operation you would like (meaning you can use $\log$ and derivatives, but using those is probably going to be inefficient).
If we are allowed to use the Gamma function:
$$\Gamma(5)\cdot(9-8)^{10} = 24$$
or if we can use the factorial and square root:
$$\left(8^{\frac{10}{5\sqrt{9}}}\right)!$$
I can probably think up some more using other special-ish functions. The way I learned $24$ we could use addition, subtraction, multiplication, division, exponentiation, and square roots (and, of course, parentheses). I'm pretty sure there isn't a way to solve it with only those rules, although I'll keep trying.
Edit: We have
$$\sqrt{\left(8\sqrt{9}\right)^{\frac{10}{5}}} = 24$$
which uses only the "expanded standard" rules. It is the "cleanest" in my opinion of the solutions here.