I'd like to find a recursive formula giving positive integer solutions to this Diophantine equation $5L^2 - a^2 - 1 =0$
It can be seen that I need $5L^2 - 1$ to be a square of a number $\in \mathbb N$.
The problem is, I never did this before, and I don't know where and how to begin.
I would be very much satisfied with a good read on finding recursive solutions to these type of equations, too.