hello, busybox 'for' command is not working as it does on common distributions.

it says:
line 1: syntax error: Bad for loop variable
is there a special way to work with for variables in maemo??
my script run well on ubuntu

the for scripts is:
formpl:

for ((i=1;i<=$1;i++)) do mpl mp3 $i;done

mpl command works well

thanks