First of all, please use [code][/code] tags around your code, to preserve formatting and readability.
Second, your while loop doesn't do anything to change the test.
while [[ $a1 -lt $a11 ]] ; do
c=$(echo "scale=10; $c+0.005" | bc)
echo "c is $c"
If a1 is less than a11, the loop will continue indefinitely.