R49081 is prime

The late Harvey Dubner found unit Rep R49081 to be a probable prime in 1999 and reported on it in his paper [1]. Today I completed ECPP (Elliptic Curve Primailty Proving) certification and a full verification of it using Marcel Martin's excellent Primo program. The certification lasted 20 months on an AMD 3990x computer (64 cores); and verification took about 13 hours. This is the first proof of a Rep unit prime since that of R1031 in 1985 (Williams and Dubner) [2] performed on a Dubner Cruncher [3]. The new evidence surpasses my previous ECPP record at 40,000 digits [4]. The R49081 certificate will be available on the Marcel's Ellipsa website [5].

There are now 6 Rep unit primes and 5 known probable Rep unit primes; The smallest unproven is R86453 (Baxter, 2000)[2].

[1]https://www.ams.org/journals/mcom/20...01-01319-9.pdf

[2] https://primes.utm.edu/top20/page.php?id=57

[3] https://primes.utm.edu/bios/page.php?id=579

[4] https://primes.utm.edu/top20/page.php?id=27

[5] http://www.ellipsa.eu/public/primo/records.html