English
The mgf has an analytic power series expansion around v with coefficients given by the integrals μ[X^n e^{v X}]/n!.
Русский
MGF имеет аналитическое разложение в ряд вокруг v с коэффициентами μ[X^n e^{v X}]/n!.
LaTeX
$$$\text{HasFPowerSeriesAt}(\mathrm{mgf}(X, \mu), \mathrm{FormalMultilinearSeries.ofScalars}(\mathbb{R}, n \mapsto (\mu[X^n e^{v X}])/n!))\, v.$$$
Lean4
theorem hasFPowerSeriesAt_mgf (hv : v ∈ interior (integrableExpSet X μ)) :
HasFPowerSeriesAt (mgf X μ)
(FormalMultilinearSeries.ofScalars ℝ (fun n ↦ (μ[fun ω ↦ X ω ^ n * exp (v * X ω)] : ℝ) / n !)) v :=
by
convert (analyticAt_mgf hv).hasFPowerSeriesAt
rw [iteratedDeriv_mgf hv]