Fℓ⁡(η,ρ)=Cℓ⁡(η)⁢ρℓ+1⁢ⅇ∓ⅈ⁢ρ⁢M⁡(ℓ+1∓ⅈ⁢η,2⁢ℓ+2,±2⁢ⅈ⁢ρ),