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Old 2020-01-25, 18:03   #298
JeppeSN's Avatar
Jan 2016

25·5 Posts

Originally Posted by Dr Sardonicus View Post
For the remaining value, 6*2^5523860 + 1, I didn't look far enough to find any factors, but I didn't look all that far. Has (as I suspect) someone already found a factor by trial division, or otherwise shown it to be composite?
Yes, your number 3*2^5523861 + 1 is composite, because PrimeGrid has established the primality status of all numbers 3*2^n ± 1 for n up to over 15.5 million, see their page stats_321_llr. We do not have access to their data, but if we ask them, they can maybe tell us if this candidate was eliminated during sieving (they may have the prime factor then) or during primality testing and double checking (they may have the residue then). However, I guess it is of limited interest. /JeppeSN
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