We derive a deterministic covering theorem: for any even N ≥ 8, the interval 1,N is covered by Y -smooth numbers and their complements with respect to N + 1 provided Y ≥ ⌈N/3⌉. We further identify the unique obstruction type just below this threshold: in the window ⌊N/5⌋ Y . Motivated by computation, we propose a strengthened (well-balanced) Lemoine-type conjecture asserting that such representations can be chosen with both primes located within a polylogarithmic distance of N/3.
Peter Upham (Mon,) studied this question.
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