PPL 157 / 177 permanent IDsPrize Problem Ledger · PPLChecked 2026.07.26
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Prize Problem LedgerIndependentPPL 157Shallit #7 · Are primitive binary words context-free?

Permanent problem IDPPL 157

Source-statedIndependentconjecture

Formal languages

Shallit #7 · Are primitive binary words context-free?

Determine whether the language of primitive—non-power—words over the binary alphabet is context-free.

automata theorytheoretical computer scienceformal languages
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The problem

Determine whether the language of primitive—non-power—words over the binary alphabet is context-free.

Open since2014source-stated by 2014
Last checked2026.07.26Catalog verification
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Reward offers

Offer 01£200Jeffrey 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.

Award source ↗Rules ↗
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Sources & reading

2 unique reference linksSponsor’s official problem slides Claim or award rules
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