Organisateurs: Michel Balazard (CNRS, Laboratoire Poncelet) , Michael Tsfasman (CNRS, Laboratoire Poncelet, Institut des Probl mes de Transmission de l'Information) , Alexey Zykin (Laboratoire Poncelet, Haute Ecole d'Economie) . ... Informations g n rales . ... We show that when averaging over $q$ in certain ranges, specific values of $a$ give rise to greater or smaller amounts of primes in the progressions $a \bmod q$, depending on the arithmetic properties of $a$. Laboratoire Poncelet . ...