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Research notes on every problem, and a library of the papers behind them. Built from the open erdos repository.

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1977_11_01_erdos_newman: Theorem 2 of Erdős and Newman (1977) bounds below the smallest basis of most n-element subsets of [N]; glued along a dyadic sequence it gives a density-zero set with no basis of size o(N^{1/2}), a negative answer.

2025_12_25_barreto: A direct construction, posted on 2025-12-25 and formalized in Lean 4, of a density-zero set A lying in B+B for no B with counting function o(N^{1/2}); its Lean disproof was built here.