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Unverified
Universal Positivity Set
Can one construct an infinite recursively enumerable set , for which one can decide: given any linear recurrence sequence , whether , s.t. ? In other words: is there a set of indices for which the positivity problem is decidable? The analogous question where is replaced by has a positive answer for simple sequences; Luca, Ouaknine and Worrell have constructed such a set explicitly (called the universal Skolem set).
