Take a polynomial with integer coefficients. How many primes divide each of its values? Sieves can answer many questions on the distribution of the number of primes dividing numbers in a sequence, but generally fail at getting the finest detail: it is very difficult to distinguish between numbers with an even number of prime factors and numbers with an odd number of prime factors. If the sequence is thin - which is the case if we are speaking of the sequence of values represented by a polynomial of degree greater than the number of variables - then the problem of making such a distinction was until recently thought to be hopeless.

Quite recently, Iwaniec, Friedlander and Heath-Brown developed techniques to capture primes in fairly thin sequences. We will show how to adapt them to prove the equidistribution of parity for f(x,y) homogeneous of degree 3: such a polynomial f takes values with an even number of prime factors as often as values with an odd number of prime factors.