Answer
$n=1.127(3.544)^{t}$ million members,
where t = years after the start of $2005$.
Work Step by Step
Using desmos.com, we enter the table with variables $t$ and $n$.
We enter in a free cell
$n\sim Ab^{t}$
place tick in "log mode" to obtain an exponential regression formula tying P to t, and the calculator returns (see image):
$A=1.127, b=3.544$
with the correlation coefficient $r$ being relatively close to $1$, indicating a good fit.
The model is
$n=1.127(3.544)^{t}$ million members,
where t = years after the start of $2005$.
