Power series expansion involving Lambert-W function Need to power series expand this term:
$ -\frac{e}{2z} W\left(\frac{-2z}{e^2} \right) \left( \log \left( - \frac{e}{2z} W \left( \frac{-2z}{e^2}\right) \right) -1 \right)$
I tried expanding this with Wolfram but it doesn't give me Higher Order Terms. Can anyone with Maple/Mathematica help out with this? I'm working on doing this by hand but it's gonna be tedious from the looks of it. Any suggestions welcome!!
 A: Use the MATHEMATICA commands
f = -E/(2 z) ProductLog[-2 z/E^2] (Log [-E/(2 z) ProductLog[-2 z/E^2]] - 1)
Series[f, {z, 1, 10}]//N
and you will obtain
$$
f(z)=-0.880194-0.22445 (z-1.)-0.153651 (z-1.)^2-0.164248 (z-1.)^3-0.224172 (z-1.)^4-0.355448 (z-1.)^5-0.622729 (z-1.)^6-1.17077 (z-1.)^7-2.31929
   (z-1.)^8-4.78304 (z-1.)^9-10.1829 (z-1.)^{10}+O\left((z-1.)^{11}\right)
$$
or if you prefer the lenghty form (only four therms)
$$
f(z) = \frac{1}{2} e W\left(-\frac{2}{e^2}\right) \left(W\left(-\frac{2}{e^2}\right)+2\right)-\frac{1}{2} \left(e W\left(-\frac{2}{e^2}\right)^2\right)
   (z-1)+\frac{e W\left(-\frac{2}{e^2}\right)^3 (z-1)^2}{2 W\left(-\frac{2}{e^2}\right)+2}-\frac{\left(e W\left(-\frac{2}{e^2}\right)^4 \left(3
   W\left(-\frac{2}{e^2}\right)+4\right)\right) (z-1)^3}{6 \left(W\left(-\frac{2}{e^2}\right)+1\right)^3}+\frac{e W\left(-\frac{2}{e^2}\right)^5
   \left(2 W\left(-\frac{2}{e^2}\right) \left(6 W\left(-\frac{2}{e^2}\right)+17\right)+25\right) (z-1)^4}{24
   \left(W\left(-\frac{2}{e^2}\right)+1\right)^5}+O\left((z-1)^5\right)
$$
etc.
You can also use the fact
$$
f(z) = y(z)(\ln y(z) -1)
$$
with 
$$
y(z) = -\frac{e W\left(-\frac{2 z}{e^2}\right)}{2 z}
$$
and 
$$
y_0 = y(1) = -\frac{1}{2} e W\left(-\frac{2}{e^2}\right)
$$
and then find the expansion for $y$. This can be done with MATHEMATICA or with bare  hand.
