Schröder–Hipparchus number
In combinatorics, the Schröder–Hipparchus numbers form an integer sequence that can be used to count the plane trees with a given set of leaves, the ways of inserting parentheses into a sequence, and the ways of dissecting a convex polygon into smaller polygons by inserting diagonals. These numbers begin 1, 1, 3, 11, 45, 197, 903, 4279, 20793, 103049, ...
Source: Wikipedia — Schröder–Hipparchus number (CC BY-SA 4.0)