theorem extracted_formal_statement_30 {n : ℕ} (f : ℤ → Signs n → ℝ) :
  ∑ σ, (fun σ' => f (↑σ'.1) σ'.2) ((Fin.snocEquiv fun x => { x // x ∈ {-1, 1} }).symm σ) =
    ∑ σ, f (↑(σ ↑n)) (Fin.init σ) := sorry

State before:
n : ℕ
f : ℤ → Signs n → ℝ
⊢ ∑ σ, (fun σ' => f (↑σ'.1) σ'.2) ((Fin.snocEquiv fun x => { x // x ∈ {-1, 1} }).symm σ) = ∑ σ, f (↑(σ ↑n)) (Fin.init σ)

Tactic: simp

State after:

Relevant lemmas: