May I reserve the Primo run to verify primality of the M51487 cofactor?

[QUOTE=VBCurtis;497940]May I reserve the Primo run to verify primality of the M51487 cofactor?[/QUOTE]
I think you just did, unless anyone objects. 
[QUOTE=VBCurtis;497940]May I reserve the Primo run to verify primality of the M51487 cofactor?[/QUOTE]
Should easily make it into [url]https://primes.utm.edu/top20/page.php?id=49[/url] 
[QUOTE=axn;497947]Should easily make it into [url]https://primes.utm.edu/top20/page.php?id=49[/url][/QUOTE]
Mersenne numbers are the b=2 special cases of generalized repunits (b[SUP]p[/SUP] − 1) / (b − 1). I compared Chris Caldwell's [URL="https://primes.utm.edu/top20/page.php?id=49"]list of Mersenne PRP cofactors[/URL], where the largest is not quite 20,000 digits, and his [URL="https://primes.utm.edu/top20/page.php?id=16"]list of generalized repunit PRPs[/URL], where the digit lengths go up to 95,000 digits. The generalized repunit PRPs in the list all have large b, in the thousands or tens of thousands. Nearly all of the primality certificates are by Tom Wu. Is it somehow generally true that for larger b it is easier to prove primality of (b[SUP]p[/SUP] − 1) divided by some divisor? And perhaps easier to find PRPs in the first place? However, looking at the [URL="http://www.primenumbers.net/prptop/prptop.php"]Lifchitz list of top PRPs[/URL], however, the top 1 and 2 are Wagstaff (repunit with b=−2), numbers 4, 5, 6, 8 and 14 are Mersenne cofactors (repunit with b=2), number 11 is a repunit PRP with b=−13, number 12 is a repunit PRP with b=5, etc. I don't see any large b bases in the top rankings. 
[QUOTE=GP2;497953]Mersenne numbers are the b=2 special cases of generalized repunits (b[SUP]p[/SUP] − 1) / (b − 1).
I compared Chris Caldwell's [URL="https://primes.utm.edu/top20/page.php?id=49"]list of Mersenne PRP cofactors[/URL], where the largest is not quite 20,000 digits, and his [URL="https://primes.utm.edu/top20/page.php?id=16"]list of generalized repunit PRPs[/URL], where the digit lengths go up to 95,000 digits. The generalized repunit PRPs in the list all have large b, in the thousands or tens of thousands. Nearly all of the primality certificates are by Tom Wu. Is it somehow generally true that for larger b it is easier to prove primality of (b[SUP]p[/SUP] − 1) divided by some divisor? And perhaps easier to find PRPs in the first place? However, looking at the [URL="http://www.primenumbers.net/prptop/prptop.php"]Lifchitz list of top PRPs[/URL], however, the top 1 and 2 are Wagstaff (repunit with b=−2), numbers 4, 5, 6, 8 and 14 are Mersenne cofactors (repunit with b=2), number 11 is a repunit PRP with b=−13, number 12 is a repunit PRP with b=5, etc. I don't see any large b bases in the top rankings.[/QUOTE] The big proven GRUs are done with CHG or KP proof methods where a great deal of finding and proving the factors of N^21 is done, whereas the Mersenne cofactors are purely ECPP. 
[QUOTE=GP2;497953]Is it somehow generally true that for larger b it is easier to prove primality of (b[SUP]p[/SUP] − 1) divided by [STRIKE]some[/STRIKE] algebraic divisor? [/QUOTE]
(b[SUP]p[/SUP] − 1) / (b − 1)  1 = x * (b[SUP]p1[/SUP] − 1), so if p1 is fairly smooth, and some of the cofactors happen to be prime, then you have a path to N1 proof. Same for N+1. What we see at the top [url]https://primes.utm.edu/top20/page.php?id=16[/url], are enriched with harder proof methods but if you use [url]https://primes.utm.edu/primes/search.php[/url], and search for Text Comment = Generalized Repunit, Type = all, Maximum number of primes to output = 2000, you will find tons of simple N+1 proofs, as well. 
[QUOTE=VBCurtis;497940]May I reserve the Primo run to verify primality of the M51487 cofactor?[/QUOTE]
It has been a while since I've used Primo; I forgot that it lacks commandline interface, and I have only SSH access to my 40thread workstation. I should put some time into relearning Primo usage on smaller inputs before I tackle a multimonth job; unreserving this cofactor. 
[QUOTE=VBCurtis;497996]... unreserving this cofactor.[/QUOTE]
Reserving M51487 cofactor. Should be a few weeks to a month. 
Has anyone tried the [c]primecert[/c] and [c]primecertexport[/c] functions in recent PARI/GP versions? The documentation says it can create a Primo v. 4 certificate. How does the speed compare with the actual Primo program?

I was able to configure Bash for Windows to run Primo on Windows 10.
I performed the following steps in Ubuntu 18.04 on Bash for Windows: 1) Install Xming (the X server) 2) Open Bash for Windows 3) Type [FONT="Courier New"]sudo aptget update[/FONT] 4) Type [FONT="Courier New"]sudo aptget upgrade[/FONT] 5) Type [FONT="Courier New"]sudo aptget install gdkpixbuf2.00[/FONT] 6) Type [FONT="Courier New"]sudo aptget install libgtk2.0dev[/FONT] 7) Type [FONT="Courier New"]sudo aptget install xdgutils[/FONT] 8) Open .bashrc (I used nano), add the following line at the end of this file: [FONT="Courier New"]export DISPLAY=:0[/FONT] and save it. 9) Download the latest version of Primo and decompress it in a directory that can be seen on Bash for Windows 10) Close Bash for Windows 11) Ensure that Xming is running 12) Open Bash for Windows 13) Run Primo and enjoy. 
[QUOTE=Batalov;498000]Reserving M51487 cofactor. Should be a few weeks to a month.[/QUOTE]
Congrats for the proof. [url]https://primes.utm.edu/primes/page.php?id=125757[/url] 
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