Euler had already become famous for finding the values of these functions at positive even integers (including the Basel problem), and he was attempting to find the values at the positive odd integers (including Apéry's constant) as well, a problem that remains elusive today.
Euler xa se fixera famoso por atopar os valores destas funcións para enteiros pares positivos (incluíndo o problema de Basilea) e tentou atopar os valores para enteiros impares positivos (incluíndo a constante de Apéry): este último problema aínda está sen resolver hoxe en día.