The shell command
"/l/www/moodle/filter/tex/mimetex.linux" -e "/m/floppy/avle/moodledata/filter/tex/1cfad354193570f43b9cdcbdc2ba3d3b.gif" -- '\Large a_{n+1}-a_{n}=d \text{ ja } d=vakio.'
returned status = 126
Image not found!
Please try the debugging script