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Aug24-07, 10:14 PM
Sci Advisor
PF Gold
Hurkyl's Avatar
P: 16,091
Is it not enough to simply check modulo more primes of the form 3k+1?

I suspect you could do the computation faster if you didn't check 7, 9, 13, and 19 separately... but instead computed it once modulo 7*9*13*19, and uesd that to compute the residue modulo your other moduli. (Or even just stored an array indicating whether an element modulo 7*9*13*19 is a cube)