Well, not exactly regular NP, as was pointed out. I guess NP complete would make more sense. Although the set of problems that are easier to validate than solve

Well, not exactly regular NP, as was pointed out. I guess NP complete would make more sense. Although the set of problems that are easier to validate than solve reaches much further than NP complete; see basically any Σ in the polynomial hierarcy. It's about the existential quantifier.