title: Is there a pseudo-random number generator simple enough to do in your head?
body: <p>Are there are any pseudo-random number generators that are easy enough to do with mental arithmetic, or mental arithmetic plus counting on your fingers. Obviously this limits to fairly simple math - it needs to be something someone of average mathematical ability can do, or maybe average ability for a programmer, not a math prodigy.</p>
  
  <p>The simplest I have found is the <a href="http://en.wikipedia.org/wiki/Middle_square_method" rel="noreferrer">Middle square method</a>, but not only is it known to be a poor source of randomness, it still looks too complex to do without pencil and paper.</p>
  
  <p>If the only way to do this is by limiting the range, like maybe it only can output 8 bit numbers, that is fine. I suspect one of the standard PRNG algorithms would be simple enough in an 8 bit version, but I don't know enough to simplify any of them from the 32 bit version to an 8 bit version. (All the ones I looked at depend on specially picked seed numbers that are different depending how many bits you are working with, and usually only 32 and 64 bit examples are given.)</p>