hacker.org

did it in one line:

# convert -resize 8 -black-threshold 70% -negate stars.php.png pbm:- | sed -n 3p

I did it with zsh:

# cat pi_10e6digits.txt| sed 's;.;&\n;g' > pi_10e6_newlines.txt
# for i in {1..12} ; cat pi_10e6_newlines.txt| tail -n +$i > listpi.$i.txt
# paste listpi.{1..12}.txt| sed 's;\s;;g' | sort -n | uniq -c | grep -v " 1 "

computing time was about 10 seconds