A round table conference to be held between 20 delegates of 20…

A round table conference to be held between 20 delegates of 20 countries. In how many ways can they seated if two particular delegates are always to sit together?

This problem repeats another one in the library (at most with different numbers), so it's left out of browsing.

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #90545