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 2018-10-26, 04:11 #1 chunsonnn   Oct 2018 116 Posts Does NewPGen have a bug? I was sieving k=173 from n=1M to n=2M, and I found this message by NewPGen: p=2215115304221 divides n=1798220. However 2,215,115,304,221 is composite (that number is 8627 * 256765423), so that message should not have popped up. Why didn't NewPGen remove n=1798220 when it was at p=8627 or at p=256765423? In case anyone's wondering, I was using NewPGen version 2.82 on a Pentium 4 computer. The problem also appears on another Pentium 4 machine, so I'm pretty sure it's not a hardware problem. Thank Cristiano
2018-10-26, 04:31   #2
axn

Jun 2003

17×263 Posts

Quote:
 Originally Posted by chunsonnn I was sieving k=173 from n=1M to n=2M, and I found this message by NewPGen: p=2215115304221 divides n=1798220. However 2,215,115,304,221 is composite (that number is 8627 * 256765423), so that message should not have popped up. Why didn't NewPGen remove n=1798220 when it was at p=8627 or at p=256765423? In case anyone's wondering, I was using NewPGen version 2.82 on a Pentium 4 computer. The problem also appears on another Pentium 4 machine, so I'm pretty sure it's not a hardware problem. Thank Cristiano
p=2215115304211 divides 173*2^1798220-1

 2018-10-26, 06:28 #3 paulunderwood     Sep 2002 Database er0rr 3·1,033 Posts Isn't k=173 already sieved very deeply by PrimeGrid?
 2018-10-26, 12:01 #4 ATH Einyen     Dec 2003 Denmark 3×13×71 Posts Neither 8627 nor 256765423 is a factor of 173*2^1798220-1, so it must have been p=2215115304211 as axn pointed out.
2018-10-26, 12:08   #5
pinhodecarlos

"Carlos Pinho"
Oct 2011
Milton Keynes, UK

112·37 Posts

Quote:
 Originally Posted by paulunderwood Isn't k=173 already sieved very deeply by PrimeGrid?
Yes and tested up to n=2.04M by RPS.

 2018-10-26, 13:26 #6 rogue     "Mark" Apr 2003 Between here and the 11×509 Posts Why are you using newpgen for this form? Use srsieve/sr1sieve. They are much, much faster than newpgen for this form.

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