PPL 144 / 177 permanent IDsPrize Problem Ledger · PPLChecked 2026.07.26
Prize Problem LedgerPPL · Open reward indexAll 177 problems
Prize Problem LedgerIndependentPPL 144Shallit #12 · Kolakoski letter frequencies

Permanent problem IDPPL 144

Source-statedIndependentconjecture

Formal languages

Shallit #12 · Kolakoski letter frequencies

Do the limiting frequencies of 1 and 2 exist in the Oldenburger–Kolakoski word, and are both equal to one half?

automata theorytheoretical computer scienceformal languages
01

The problem

Do the limiting frequencies of 1 and 2 exist in the Oldenburger–Kolakoski word, and are both equal to one half?

Open since1965historical 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.

Award source ↗Rules ↗
03

Sources & reading

2 unique reference linksSponsor’s official problem slides Claim or award rules
04

Related open targets

Formal languagesShallit #18 · Shortest forbidden factor boundsPPL 150 · £200 · 14 years openFormal languagesShallit #19 · Pierce expansion lengthPPL 151 · £200 · 12 years openFormal languagesShallit #7 · Are primitive binary words context-free?PPL 157 · £200 · 12 years open