Possible Duplicate:
On the equation $(a^2+1)(b^2+1)=c^2+1$
I came across a problem: What is relation between $b$ and $c$ such that $b^2 + c^2 + b^2 c^2$ is a perfect square?
After trying few cases, I got following relations:
- $c = 2b^2$
- $c = b+1$
But it still doesn't cover all cases e.g. $(1,12),(2,21),(2,55),(3,80),(8,30)$ etc. How do I find general relation ?