- In combinatorial mathematics, the Catalan numbers are a sequence of natural numbers that occur in various counting problems, often involving recursively defined objects. They are named after the French-Belgian mathematician Eugène Charles Catalan.
- Islamic State – Khorasan Province (Wikipedia)
The Islamic State – Khorasan Province (ISIS–K or IS–KP) is a regional branch of the Salafi jihadist group Islamic State (IS) active in South-Central Asia, primarily Afghanistan and Pakistan. ISIS–K seeks to destabilize and replace current governments within historic Khorasan region with the goal of establishing a caliphate across South and Central Asia, governed under a strict interpretation of Islamic sharia law, which they plan to expand beyond the region.