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Old 2010-02-10, 14:34   #67
Rincewind's Avatar
Oct 2006

103 Posts

Originally Posted by geoff View Post
If you are sieving sequences k*b^n+/-1 then internally sr2sieve converts each one into a number of subsequences of the form (k*b^d)*(b^Q)^m+/-1, where 0 <= d < Q, m = n\Q, and Q is some value chosen using a method that involves a rough approximation of the work needed for each different value of Q considered.

(You can get a list of the values considered and the estimated work by using the -vv switch.)

Normally sr2sieve chooses a good value for Q automatically, but sometimes (usually when there are a very small or very large number of sequences being sieved together) it gets it wrong, and so the -Q switch lets you set the value of Q manually in those cases.

It happens that, for the last remaining sequence this project is sieving, the optimal value for Q is 720 but sr2sieve chooses something else (180 I think). -Q720 just sets the optimal value manually.
OK, thank you for the answers
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