Problem

Source: MEMO 2023 I2

Tags: combinatorics, MEMO2023, geometry



Find all positive integers $n \geq 3$, for which it is possible to draw $n$ chords on a circle, with their $2n$ endpoints being pairwise distinct, such that each chords intersects exactly $k$ others for: (a) $k=n-2$, (b) $k=n-3$.