Abstract:
In this paper, we deal with the equation
$(a^{n}-2)(b^{n}-2)=x^{2}$,
$2\leq a<b$,
and
$a,b,x,n\in\mathbb{N}$.
We solve this equation for
$(a,b)\in\{(2,10),(4,100),(10,58),(3,45)\}$.
Moreover, we show
that
$(a^{n}-2)(b^{n}-2)=x^{2}$
has no solution
$n,x$
if
$2|n$
and
$\gcd(a,b)=1$.
We also give a conjecture which says that the equation
$(2^{n}-2)((2P_{k})^{n}-2)=x^{2}$
has only the solution
$(n,x)=(2,Q_{k})$,
where
$k>3$
is odd
and
$P_{k},Q_{k}$
are the Pell and Pell Lucas numbers, respectively.
We also
conjecture that if the equation
$(a^{n}-2)(b^{n}-2)=x^{2}$
has a solution
$n,x,$
then
$n\leq6$.
Keywords:Pell equation, exponential Diophantine equation, Lucas sequence.