math_fact: 280 is the number of ways 18 people around a round table can shake hands in a non-crossing way, up to rotation.
trivia: 280 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
historical_date: October 6th is the day in 1976 that New Premier Hua Guofeng orders the arrest of the Gang of Four and associates and ends the Cultural Revolution in the People's Republic of China.