文摘
For a fixed quadratic irreducible polynomial f with no fixed prime factors at prime arguments, we prove that there exist infinitely many primes p such that f(p) has at most 4 prime factors, improving a classical result of Richert who requires 5 in place of 4. Denoting by \(P^+(n)\) the greatest prime factor of n, it is also proved that \(P^+(f(p))>p^{0.847}\) infinitely often.