Fatto matematico: 2587 is a value of n for which f(n) + f(n+1) divides s(n) + s(n+1).
Trivia: 2587 is an unremarkable number.
Data storica: January 30th is the day in 1667 that the Polish-Lithuanian Commonwealth cedes Kiev, Smolensk, and left-bank Ukraine to the Tsardom of Russia in the Treaty of Andrusovo.