What's the arithmetic form of the value $k$ in this graph?

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https://www.desmos.com/calculator/m1kaifseq0

in order to get the control points to line up properly, I had to use trial and error to determine the value for this strange constant $k$ at the bottom of my formula sheet. It's approximately $2.299113817$. I have no idea what the arithmetic representation of it is. If anyone can provide some insight to give me some peace of mind, I would greatly appreciate it.

Analytically, $k$ ought to be the value such that $$c+\frac{a\left(c-b\right)}{\ln2}\frac{2^{-\frac{k}{a}}-1}{k} =\frac{c+b}{2}$$

for any arbitrary $a$, $b$, and $c$.

Edit: I've simplified the equation down somewhat to remove the unnecessary constants, and am left with this:

$$\frac{1}{k2^{k}}-\frac{1}{k}=-\frac{\ln2}{2}$$

I'm not sure if this is easier to solve or not

Further edit: according to Wolfram Alpha, the solution is

$$\frac{2+W\left(-\frac{2}{e^{2}}\right)}{\ln2}$$

which is indeed not pretty...

Final edit: I have decided to define the constant like so in my graph:

$$k=\frac{2+\sum_{m=1}^{66}\frac{\left(-m\right)^{m-1}}{m!}\left(-\frac{2}{e^{2}}\right)^{m}}{\ln2}$$

its not pretty, but it is accurate...