Prove SeymourSecondNeighborhood (openai/math family 173: Seymour's second-neighborhood conjecture) in Lean 4…

Prove SeymourSecondNeighborhood (openai/math family 173: Seymour's second-neighborhood conjecture) in Lean 4…: a task in openai/math as Harbor environments (Harbor dataset). Context: this statement belongs to family 173 of the release, Seymour's second-neighborhood conjecture (Combinatorics). The…

The task

Context: this statement belongs to family 173 of the release, *Seymour's second-neighborhood conjecture* (Combinatorics). The family as a whole: Proves Seymour's second-neighborhood conjecture: every nonempty finite oriented graph has a vertex with at least as many vertices at directed distance exactly two as at…

Part of raising-heart/openai-math.