English
A specialized form of the projection formula: (verschiebung^i x · verschiebung^j y).coeff (i+j) = p-powers times coefficients of x and y at zero index.
Русский
Узкую форму проективной формулы: (verschiebung^i x · verschiebung^j y).coeff(i+j) = x.coeff 0^{p^j} · y.coeff 0^{p^i}.
LaTeX
$$$ (verschiebung^{i} x \cdot verschiebung^{j} y).coeff (i + j) = x.coeff 0^{p^{j}} \cdot y.coeff 0^{p^{i}} $$$
Lean4
theorem iterate_verschiebung_coeff (x : 𝕎 R) (n k : ℕ) : (verschiebung^[n] x).coeff (k + n) = x.coeff k := by
induction n with
| zero => simp
| succ k ih => rw [iterate_succ_apply', Nat.add_succ, verschiebung_coeff_succ]; exact ih