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Old 2014-05-14, 07:48   #7
Romulan Interpreter
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Jun 2011

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Originally Posted by EdH View Post
Why would you only search for merges less than your number?
You don't. We check for merges in the same way you did, looking at the last number in the sequence. Historically, because they were a million and no data base available (with all the factors) some lists were made, which record for example "the first 10 digit number" reached by a sequence. Most of the million sequences do not reach a 10 digits term, but if your (new) sequence do, you look in the list if it is a merge. Very easy to check. Then, a 30-digits list was done, or a 50 digits list. This way one don't need to search all the factor data base (in fact, we don't have such a database, FDB is bloody to search). The advantage of a list is the fact that such list is fixed, once the remaining sequences pass over the threshold, and do not need to be maintained, except rarely (if a sequence goes under 50 digits, for example, and came back over it, a new term will be added to the list). There was a list of "first reach 100 digits" too, but that is not used so much anymore, because at the time when the "remaining sequences" reached 100 digits, very few survived, and a list with last term is easy to get from the DB now. The problem is that the DB is not very well maintained, Sid is always busy when you need him... People report the results seldom, they don't report downdrivers till the downrun end, because they are afraid of ddhunters, etc.

Dubslow's site was a good resource, but is down since some time. Therefore I keep my own lists. I would like to host/mirror Dubslow's page, for example, it will not be a big deal of trafic, it may not be available 24/7, but most of the time will be available, and any positive number is better than zero... but I can't contact him. Also, I am sure other people here could host that page too, better than me...

Couldn't any one of the above numbers have been worked by someone, who did not realize they were also working 154548?
Only if he didn't know what he was doing. The sequences in your list, once reported as mergers (all were known), they are eliminated from the reservation list. For example, I start working 279936, because I liked it (it is 6^7, perfect number at odd power, blah blah) which, after a lot of adventures, merged with other sequences, the smaller of them being 95280. I kept the reservation for 95280, but the other were erased from the list. They are not available for reservation anymore. For the same reason you can not reserve for example sequence 396, neither is this listed as one of Lehmer fives, because is a merger with a lower sequence (276) and therefore 396 does not appears in the list anymore. Of course, someone can work the sequence 396, but only if he doesn't know what he is doing. Or if he poaches.

Last fiddled with by LaurV on 2014-05-14 at 07:51
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