So for those who were curious, the by-line at the top of the blog is the beginning description of a Markov sequence or Markov chain. It’s a sequence of random variables X1, X2, X3, … with the property that, given the present state, the future and past states are independent. While that may not sound very interesting, the Wikipedia entry notes that Markov chains are used in Google’s PageRank, speech recognition, generating random numbers, and in Bayesian inference. The last one is the email tie-in because of its use in sorting out bulk spam emails from the emails you want to get.