TITLE: Assistance with understanding parent/child relationships in Pythagorean Triples
QUESTION [17 upvotes]: I want to start by apologising for what is probably a weak attempt at a question on a site like this, but I'm having trouble understand a concept that doesn't seem to be properly explained elsewhere - perhaps someone can put it in layman's terms.
I've been trying to understand the idea on Wikipedia that discusses Pythagorean Triple
- namely the section entitled Parent/child relationships. It talks about a Swedish man called Berggren who devised a set of equations that would allow you to determine the children of this parental triple. Each parent created 3, which in turn created 3 and so on.
When I started running the code, I couldn't pick up a certain triple - (200, 375, 425) 
Basically, I wondered if someone could provide a little clarification. Is it either that...

My code is wrong, it's definitely
possible to get to that triple from
a starting point of (3,4,5). 
I haven't understood what Berggren
used these equations for, and I need
to back and read it properly.

Any clarification would be superb,
Thanks
P.S - Could someone also tag this appropriately? I have no idea which subject it comes under.

REPLY [4 votes]: The Classic Tree shown above was probably first found by B. Berggren in 1933. Recently, an entirely New Tree was found. [see: H. Lee Price (2008).The Pythagorean tree: A new species. ArXiv e-prints, arXiv:0809.4324,  pp 14.]