I see a few patterns...

like...

4 5 8

4+5 = 9 - 1 = 8

giving something like:

2 4 5 8 12 19 30

So a wild guess at '?' would be 499. It does make a pattern atleast.

I don't know about x^2+y^2=z^2, as:

sqr(4^2+5^2) =+/-sqr(41)