Almost-prime polynomials at prime arguments

We improve Irving's method of the double-sieve [7] by using the DHR sieve. By extending the upper and lower bound sieve functions into their respective non-elementary ranges, we are able to make improvements on the previous records on the number of prime factors of irreducible polynomials at prime arguments. In particular, we prove that irreducible quadratics over Z satisfying necessary local conditions are P-4 infinitely often. (C) 2017 Elsevier Inc. All rights reserved.