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2021-09-26, 14:02   #26
Dr Sardonicus

Feb 2017
Nowhere

2×3×23×37 Posts

Quote:
 Originally Posted by Batalov I did test for the 4th AP term. for the lower AP-3, 5^2 | A(4) for the higher AP-3, I have not found a trivial factor, but it is composite. A1 = 5606879602425*2^1290000-1 prime A2 = 33*2^2939063-1 prime A3 = 33*2^2939064-5606879602425*2^1290000-1 prime A4 = 99*2^2939063-5606879602425*2^1290001-1 composite
So, A3 is the top, as I originally guessed and you confirmed. Obviously, I don't know which end is up.

If the common difference is d, the AP-3 is A3 - 2d, A3 - d, A3.

I assume A4 was checked for small factors, then subjected to a compositeness test that proved it to be composite, but did not reveal any factors.