Creating AppleScript for keystrokes
To start off, the number 1.0E+300 is a really REALLY big number.  That's  more than the number of atoms in the entire universe by several orders.

Your script isn't far off.  To press "c" thirteen times, you can either do this:

repeat 13 times
    tell application "System Events" to keystroke "c"
    -- delay 0.1
end repeat


(you potentially need a small delay there to register individual keystrokes, but you can try it without and see which works);

or you can do this:

tell application "System Events" to keystroke "ccccccccccccc"


which is the equivalent of the repeat loop without the delay.

The left and right arrow keys are key code 123 and key code 124, respectively.  So, adding those in between the keystrokes:

tell application "System Events"
    keystroke "ccccccccccccc"
    delay 0.1
    key code 123 -- left arrow
    delay 0.1
    keystroke "ccccccccccccc"
    delay 0.1
    key code 124 -- right arrow
end tell


OR:

tell application "System Events"
    repeat 13 times
        keystroke "c"
        delay 0.1
    end repeat

    key code 123 -- left arrow
    delay 0.1

    repeat 13 times
        keystroke "c"
        delay 0.1
    end repeat

    key code 124 -- right arrow
end tell


Finally, doing this ad infinitum on a loop at 1.7 second intervals, will produce something resembling this:

tell application "System Events" to repeat
    repeat 13 times
        keystroke "c"
        delay 0.1
    end repeat

    key code 123 -- left arrow
    delay 0.1

    repeat 13 times
        keystroke "c"
        delay 0.1
    end repeat

    key code 124 -- right arrow

    delay 1.7
end repeat


Note that the outside-most repeat loop has no while, until, or times to limit its continuation.  It will loop forever, until you stop the script manually.

I also didn't factor the 0.1-second delays into the overall 1.7-second delay.  The smaller delays will exceed 1.7 seconds in total, but I'll let you adjust the timings to your needs.