For an odd positive integer $n$
, define $$ \begin{align*}P_n(x, y) = \sum\limits_{\substack{0 \leq k \leq n\\k \text{ is even}}}(-1)^{\frac{k}{2}}\binom{n}{k}x^{n - k - 1}y^k. \end{align*} $$
We prove that, for $n \geq 5$
, the Thue equation $P_n(x, y) = 1$
has exactly two solutions in integers $x$
and $y$
, namely, $(1, 0)$
and $(-1, 0)$
, and that the Thue equation $P_n(x, y) = -1$
has no solutions. Our result is a consequence of the famous theorem of Bilu, Hanrot, and Voutier on Lucas sequences.