PPL 142 / 177 permanent IDsPrize Problem Ledger · PPLChecked 2026.07.26
Prize Problem LedgerIndependentPPL 142Shallit #1 · Improve the separating-words upper bound

Permanent problem IDPPL 142

Source-statedIndependentconjecture

Formal languages

Shallit #1 · Improve the separating-words upper bound

Improve Robson’s O(n²⁄⁵(log n)³⁄⁵) upper bound on the number of DFA states needed in the worst case to separate two distinct length-n words.

automata theorytheoretical computer scienceformal languages
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The problem

Improve Robson’s O(n²⁄⁵(log n)³⁄⁵) upper bound on the number of DFA states needed in the worst case to separate two distinct length-n words.

Open since1989historical source
Last checked2026.07.26Catalog verification
02

Reward offers

Offer 01£100Jeffrey Shallit
Personal offer

Personal cash offer stated in Shallit’s official talk. The live talks page records subsequent updates, including a paid solution to one omitted problem; confirm claim procedure with the sponsor before relying on the award.

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Sources & reading