sum_(k = 0)^m (ϕ_k(x) ϕ_k(y))/γ_k = (ϕ_(m + 1)(x) ϕ_m(y) - ϕ_m(x) ϕ_(m + 1)(y))/(a_m γ_m(x - y), ) where ϕ_k(x) are orthogonal polynomials with weighting function W(x) such that γ_m congruent integral[ϕ_m(x)]^2 W(x) d x, and a_k congruent A_(k + 1)/A_k with A_k is the coefficient of x^k in ϕ_k(x).

Christoffel formula | orthogonal polynomials