Existence of a productive set that is not completely productive
Determine whether there exists a productive set that is not completely productive, where a productive set is a set A ⊆ N admitting a recursive function f such that W_n ⊆ A implies f(n) ∈ A \ W_n, and a completely productive set is a set A ⊆ N admitting a recursive function g such that g(n) ∈ A if and only if g(n) ∉ W_n for every n ∈ N.
References
It is not known whether there is a productive set that is not c.p.
— Beyond the Turing threshold: Productive grammars generate essentially undecidable languages
(2609.11385 - Augusto, 10 Sep 2026) in Immediately following Proposition 37, Section 2.2 (Productive Sets)