We denote the number of positive divisors of a positive integer m by d(m) and the number of distinct prime divisors of m by ω(m). Let k be a positive integer. Prove that there exist infinitely many positive integers n such that ω(n)=k and d(n) does not divide d(a2+b2) for any positive integers a,b satisfying a+b=n. quadraticsnumber theoryDivisorsCombinatorial Number TheoryEGMOEGMO 2014