For half-odd-integer values of the exponent parameters:

 31.8.1 $\displaystyle\beta-\alpha$ $\displaystyle=m_{0}+\tfrac{1}{2},$ $\displaystyle\gamma$ $\displaystyle=-m_{1}+\tfrac{1}{2},$ $\displaystyle\delta$ $\displaystyle=-m_{2}+\tfrac{1}{2},$ $\displaystyle\epsilon$ $\displaystyle=-m_{3}+\tfrac{1}{2}$, $m_{0},m_{1},m_{2},m_{3}=0,1,2,\dots$,

the Hermite–Darboux method (see Whittaker and Watson (1927, pp. 570–572)) can be applied to construct solutions of (31.2.1) expressed in quadratures, as follows.

Denote $\mathbf{m}=(m_{0},m_{1},m_{2},m_{3})$ and $\lambda=-4q$. Then

 31.8.2 $w_{\pm}(\mathbf{m};\lambda;z)=\sqrt{\Psi_{g,N}(\lambda,z)}\*\mathop{\exp\/}% \nolimits\!\left(\pm\frac{i\nu(\lambda)}{2}\int_{z_{0}}^{z}\frac{t^{m_{1}}(t-1% )^{m_{2}}(t-a)^{m_{3}}dt}{\Psi_{g,N}(\lambda,t)\sqrt{t(t-1)(t-a)}}\right)$

are two independent solutions of (31.2.1). Here $\Psi_{g,N}(\lambda,z)$ is a polynomial of degree $g$ in $\lambda$ and of degree $N=m_{0}+m_{1}+m_{2}+m_{3}$ in $z$, that is a solution of the third-order differential equation satisfied by a product of any two solutions of Heun’s equation. The degree $g$ is given by

 31.8.3 $g=\tfrac{1}{2}\max\left(2\max_{0\leq k\leq 3}m_{k},1+N-(1+(-1)^{N})\left(% \tfrac{1}{2}+\min_{0\leq k\leq 3}m_{k}\right)\right).$

The variables $\lambda$ and $\nu$ are two coordinates of the associated hyperelliptic (spectral) curve $\Gamma:\nu^{2}=\prod_{j=1}^{2g+1}(\lambda-\lambda_{j})$. (This $\nu$ is unrelated to the $\nu$ in §31.6.) Lastly, $\lambda_{j}$, $j=1,2,\ldots,2g+1$, are the zeros of the Wronskian of $w_{+}(\mathbf{m};\lambda;z)$ and $w_{-}(\mathbf{m};\lambda;z)$.

By automorphisms from §31.2(v), similar solutions also exist for $m_{0},m_{1},m_{2},m_{3}\in\Integer$, and $\Psi_{g,N}(\lambda,z)$ may become a rational function in $z$. For instance,

 31.8.4 $\displaystyle\Psi_{1,2}$ $\displaystyle=z^{2}+\lambda z+a,$ $\displaystyle\nu^{2}$ $\displaystyle=(\lambda+a+1)(\lambda^{2}-4a)$, $\mathbf{m}=(1,1,0,0)$,

and

 31.8.5 $\displaystyle\Psi_{1,-1}$ $\displaystyle=\left(z^{2}+(\lambda+3a+3)z+a\right)/z^{3},$ $\displaystyle\nu^{2}$ $\displaystyle=(\lambda+4a+4)\left((\lambda+3a+3)^{2}-4a\right)$, $\mathbf{m}=(1,-2,0,0)$. Symbols: $z$: complex variable, $\nu$: real or complex parameter, $a$: complex parameter, $\lambda=-4q$ and $\Psi_{g,N}(\lambda,z)$: polynomial Referenced by: Equation (31.8.5) Permalink: http://dlmf.nist.gov/31.8.E5 Encodings: TeX, TeX, pMML, pMML, png, png Errata (effective with 1.0.7): Originally the first term on the right side of the equation for $\Psi_{1,-1}$ was $z^{3}$. The correct term is $z^{2}$. Reported 2013-07-25 by Christopher Künstler See also: info for 31.8

For $\mathbf{m}=(m_{0},0,0,0)$, these solutions reduce to Hermite’s solutions (Whittaker and Watson (1927, §23.7)) of the Lamé equation in its algebraic form. The curve $\Gamma$ reflects the finite-gap property of Equation (31.2.1) when the exponent parameters satisfy (31.8.1) for $m_{j}\in\Integer$. When $\lambda=-4q$ approaches the ends of the gaps, the solution (31.8.2) becomes the corresponding Heun polynomial. For more details see Smirnov (2002).

The solutions in this section are finite-term Liouvillean solutions which can be constructed via Kovacic’s algorithm; see §31.14(ii).