 Discrete Wronskian

For two solutions of the linear recurrence relation $x_{n+2}+b_n{x}_{n+1}+c_n{x}_n=0$, their discrete Wronskian obeys $W_{n+1}=c_n{W}_n$. Substitute the recurrence into $p_{n+1}{q}_{n+2}-p_{n+2}{q}_{n+1}$: the $b_n$ terms cancel and the remaining expression is $c_n(p_n{q}_{n+1}-p_{n+1}{q}_n)$. Iteration gives $W_{n+1}=W_1{\prod }_{m=1}^n{c}_m$, including when some $c_m$ vanish. A nonzero discrete Wronskian proves linear independence of the two solutions.