Legendre Function of the Second Kind
The second solution Q_l(x) to the Legendre differential equation. The Legendre functions of the second kind satisfy the same recurrence relation as the Legendre polynomials. The Legendre functions of the second kind are implemented in the Wolfram Language as LegendreQ[l, x]. The first few are Q_0(x) | = | 1/2 ln((1 + x)/(1 - x)) Q_1(x) | = | x/2 ln((1 + x)/(1 - x)) - 1 Q_2(x) | = | (3x^2 - 1)/4 ln((1 + x)/(1 - x)) - (3x)/2 Q_3(x) | = | (5x^3 - 3x)/4 ln((1 + x)/(1 - x)) - (5x^2)/2 + 2/3.