Cn(λ)⁡(cos⁡θ1⁢cos⁡θ2+sin⁡θ1⁢sin⁡θ2⁢cos⁡ϕ)=∑ℓ=0n22⁢ℓ⁢(n-ℓ)!⁢2⁢λ+2⁢ℓ-12⁢λ-1⁢((λ)ℓ)2(2⁢λ)n+ℓ⁢(sin⁡θ1)ℓ⁢Cn-ℓ(λ+ℓ)⁡(cos⁡θ1)⁢(sin⁡θ2)ℓ⁢Cn-ℓ(λ+ℓ)⁡(cos⁡θ2)⁢Cℓ(λ-12)⁡(cos⁡ϕ),