I get the following errors:

2 errors occured while generating hardcopy:

- Failed to convert TeX to PDF with command '
`cd /var/www/html/wwtmp/MA113/hardcopy/work.v6KbKDsm && /usr/bin/pdflatex >pdflatex.stdout 2>pdflatex.stderr hardcopy`

' (exit=1 signal=0 core=0). - First error in TeX log is:
! Missing \endgroup inserted. <inserted text> \endgroup l.210 \(\displaystyle{ \begin{eqnarray*} I've inserted something that you may have forgotten. (See the <inserted text> above.) With luck, this will get me unwedged. But if you really didn't forget anything, try typing `2' now; then my insertion and my current dilemma will both disappear.

The code I use for that part (within a PGML solution) is:

[`` \begin{eqnarray*}

\sum_{n= [$b]}^{\infty} \left( \frac{[$a]}{n} - \frac{[$a]}{n+1} \right) & = & \lim_{b\rightarrow\infty} \sum_{n= [$b]}^b \left( \frac{[$a]}{n} - \frac{[$a]}{n+1} \right) \\

& = & \lim_{b\rightarrow\infty} \left( \frac{[$a]}{[$b]} - \frac{[$a]}{[$b+1]} + \frac{[$a]}{[$b+1]} - \frac{[$a]}{[$b+2]} + \frac{[$a]}{[$b+2]} - \frac{[$a]}{[$b+3]} + \cdots + \frac{[$a]}{b} - \frac{[$a]}{b+1} \right) \\

& = & \lim_{b\rightarrow\infty} \left( \frac{[$a]}{[$b]} - \frac{[$a]}{b+1} \right) \\

& = & \frac{[$a]}{[$b]} - 0 \\

& = & [$sum].

\end{eqnarray*} ``]