I tweaked it like you did, and set it up running on background for 3 days... To my surprise, when I returned today its at 66,683 and running slooooow as hell (takes like a minute or so to print the next iteration).

I wonder how many loops its jumping through to get to the next answer?
On a side note: /usr/games/bin/primes got to the same result in like 5 seconds... (just outta curiosity)