The quest for randomness

@article{Anthes2011TheQF,
  title={The quest for randomness},
  author={Gary Anthes},
  journal={Commun. ACM},
  year={2011},
  volume={54},
  pages={13-15}
}
It's not easy to generate a string of numbers that lack any pattern or rule, or even to define exactly what randomness means.