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Γ₀
Γ₀ (Gamma-naught)
Limit
Notation: 3·5^e₉
The Feferman–Schütte ordinal: the first ordinal not reachable by iterating α ↦ ε_α.
CONSTRUCTION
Enumerate ε₀, ε_{ε₀}, ε_{ε_{ε₀}}, ... — iterating the epsilon-number enumerator.
SIGNIFICANCE
Γ₀ is the proof-theoretic ordinal of predicative mathematics — the limit of predicatively definable ordinals.
Recursive ordinals · ω₁ᶜᶾ boundary · rotates daily