balachmar,

Humm.. if memory serves me correctly one will not recieve credit for excluded factors.

Excluded factors are a little weird and why the client reports them I'm not sure.

The reason why excluded factors don't count is pretty simple really.
An excluded factor is not needed since another (generally) smaller factor has already be found for the same k/n pair. So basically even though its a real factor it wasn't needed because we already factored out the k/n pair.

If you look at the k/n pair that your factor sieved out you will actually see that that k/n pair does not exist in the database.

Why these factors are generated I don't know... I think it has something to do with the fact that one factor cannot factor more than 1 valid k/n pair, so if a k/n pair is found that your p matches there is no need to factor further with that p and the client moves on. I guess this makes the client a little faster. ( On why exactly, i'm not sure (recalling from memory) but I know they won't credit.)

I probably have a couple thousand of these...