How statement and proof provenance work
The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.
- Literature-sourced: the exact statement appears in a cited source; only wording and notation differ.
- AI-adapted: a semantically identical restatement of literature-sourced material, modulo indexing, notation, and boundary cases adopted by the library.
- AI-generated: a genuinely novel statement formulated by AI, with no source for the claim itself.
These labels describe origin, not correctness: citations and verification chips remain separate evidence.
The longest-suffix prefix automaton for a finite set of forbidden factors
Definition
Let be a finite alphabet and let be a finite nonempty set of nonempty words over . With as in Finite words, contiguous factors, avoidance and proper-prefix states, the prefix automaton for has state set , initial state , and the following transitions.
For and , reject the letter if the concatenation contains a factor in . Otherwise define to be the longest suffix of that belongs to , and put an edge labelled from to . This state exists because , and it is unique because suffixes of distinct lengths are distinct.
For enumeration, give every edge weight over . Different letters that induce the same transition remain parallel edges, so the associated transfer-matrix entry is the number of such letters.
Depends on
Used by
- Binary words avoiding 101 have generating function (1+x²)/(1-2x+x²-x³) Example
- Binary words avoiding 11 are counted by Fₙ₊₂ Example
- The published prefix automata extend canonically to DFAs for factor-avoidance languages Proposition
- Words over a finite alphabet avoiding finitely many nonempty factors have a rational length generating function Theorem
Dependency tree · two levels
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Sources
- R. P. Stanley, Enumerative Combinatorics, vol. 1, 2nd ed., Proposition 4.7.8 (standard reference, not scraped)