where $\phi = \frac{1+\sqrt{5}}{2}$ and $k!_F$ is the fibonorial of $k$, or the product of the first $k$ Fibonacci numbers? My hunch is that, this can be represented as a function in terms of the constant in the case where x=1, so I tried the following: $$ \begin{split} S = \sum_{k=0}^{\infty}{\...

I am much more familiar with math.SE. On that site there are explicit guidelines about LaTeX in titles and things like \displaystyle, \dfrac, \dbinom and similar are explicitly discouraged. See Guidelines for good use of $\LaTeX$ in question titles and perhaps also Why no use displaystyle in titl...

Here's a perfectly subjective position on the use of \displaystyle, \dfrac, \dbinom, &c. in question titles: If the usage of these elements is more distracting than helpful in a specific question title, they should be edited out. The same can be applied to the use of \color{...}, Emojis, a...