摘要
In this paper, we find all Fibonacci numbers which are products of two Jacobsthal numbers. Also we find all Jacobsthal numbers which are products of two Fibonacci numbers. More generally, taking $k,m,n$ as positive integers, it is proved that $F_{k}=J_{m}J_{n}$ implies that \begin{align*} (k,m,n) = &(1,1,1),(2,1,1),(1,1,2),(2,1,2),\\ & (1,2,2),(2,2,2),(4,1,3),(4,2,3),\\ & (5,1,4),(5,2,4),(10,4,5),(8,1,6),(8,2,6) \end{align*} and $J_{k}=F_{m}F_{n}$ implies that \begin{align*} (k,m,n) =&(1,1,1),(2,1,1),(1,2,1),(2,2,1),\\ & (1,2,2),(2,2,2),(3,4,1),(3,4,2),\\ & (4,5,1),(4,5,2),(6,8,1),(6,8,2). \end{align*}