Let d≥2\documentclass[12pt]{minimal}
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\begin{document}$$d \ge 2$$\end{document} be an integer which is not a square. We show that if (Fn)n≥0\documentclass[12pt]{minimal}
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\begin{document}$$(F_n)_{n\ge 0}$$\end{document} is the Fibonacci sequence and (Xm,Ym)m≥1\documentclass[12pt]{minimal}
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\begin{document}$$(X_m, Y_m)_{m\ge 1}$$\end{document} is the mth solution of the Pell equation X2-dY2=±1\documentclass[12pt]{minimal}
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\begin{document}$$X^2 -dY^2 = \pm 1$$\end{document}, then the equation Ym=Fn\documentclass[12pt]{minimal}
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\begin{document}$$Y_m = F_n$$\end{document} has at most two positive integer solutions (m, n) except for d=2\documentclass[12pt]{minimal}
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\begin{document}$$d=2$$\end{document} when it has three solutions (m,n)=(1,2),(2,3),(3,5)\documentclass[12pt]{minimal}
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\begin{document}$$(m,n)=(1,2),(2,3),(3,5)$$\end{document}.