[QUOTE=geoff;229539]Thanks, I didn't know about that project. So it looks like two projects have been working independently on some of these numbers :([/QUOTE]
Well yes, but not very many of them. I think 128 is too small an exponent to have any remaining composites in the Homogeneous Cunningham tables, so it's only 256 that might be an issue, given the current table limits (except for 3^512+2^512, which happens to be fully factored). And even that's too big an exponent for quite a few of the tables. So there are really only a handful of composites that would currently intersect with work being done on numbers of the form a^2^n + b^2^n (apparently 6, including the C149 from 8^256+5^256).
