Numbers are for computers, strings are for humans

Unless what you are processing, storing, or transmitting are, quite literally, strings that come from and are meant to be shown to humans, you should avoid processing, storing, or transmitting that data as strings. Remember, numbers are for computers, ...

We describe the recursive structures of the set of two-stack sortable permutations which avoid 132 and the set of two-stack sortable permutations which contain 132 exactly once. Using these results and standard generating function techniques, we ...

The Sorting by Prefix Reversals problem consists in sorting the elements of a given permutation $$\pi $$ with a minimum number of prefix reversals, i.e. reversals that always imply the leftmost element of $$\pi $$. A natural extension of this problem is ...