Primes $p$ such that $p-b$ Has a Large Power Factor and Few Other Prime Divisors

Abstract

We prove lower bounds for the number of primes $p\le N+b$ such that $p-b$ is divisible by $2^{k(N)}$ and has at most $k$ odd prime factors ($k\ge 2$), assuming $2^{k(N)}\le N^{\theta }$ for some $\theta >0$ depending on $k$. The proof uses a variant of Chen's method, weighted sieves, and Elliott's results on primes in arithmetic progressions with large power-factor moduli.

Some results improved, exposition revised, and a redundant section removed