This Demonstration shows how this concept can be built into an algorithm when the sequence is stored as a "trie", that is, a data structure that converts "sentences" of symbols into a tree structure by requiring that all -grams up to a certain length that appear in a sentence have as their parent "most" of that -gram, that is, all but the rightmost element of the original -gram. You select the elementary cellular automaton that generates the sentences. You select whether 3 or 4 is the maximum length of -grams examined. You further select which -gram of length 2 or more you wish to consider. And you select where you want to slice the -gram to convert it into a pseudo-bigram. The system responds with a figure showing the conditional probability of the second part of the pseudo-bigram given the first part of the bigram and a figure showing the conditional probability of the first part of the pseudo-bigram given the second part of the pseudo-bigram. The green circle shows the -gram you selected. The purple dashed -gram shows the relevant parent of that -gram and the blue dashed -grams show all appropriate children of the parent. The bottom row of the output shows how symmetric conditional probability (the mean of the products of the conditional probabilities over all possible slicings of the -gram) is done.